Allison Whittington,a pilot for the Roxche military, takes her childhood friend Wil Schultz on a flight across the border river. She pilots a small reconnaissance plane to show him the Lutoni Bridge, the only crossing between Roxche and the neighboring nation of Sou Beil. During the flight, they spot a downed aircraft on the Roxche side and land to investigate. Inside the wreckage, they find a man near death who entrusts them with a photograph and a message: he claims the war is based on a lie and that delivering these items to a person on the Sou Beil side could end the conflict. Allison and Wil accept the mission despite the risks. Roxche military police arrive to secure the crash site, and the pair realize they must evade their own army to carry out the man’s request. They escape and race toward the bridge, with military vehicles in pursuit. Under machine-gun fire from both sides, Allison flies the plane across the narrow bridge, but enemy anti-aircraft fire damages the aircraft. The plane crashes into the river on the Sou Beil side, but Allison and Wil survive and swim to shore. Exhausted, they emerge from the water only to be surrounded by Sou Beil soldiers pointing rifles at them. The episode ends with the soldiers demanding to know their identities, leaving the fate of the message and their mission uncertain.

Allison and Wil land their seaplane on a forest river,carrying a young boy named Carlo. Sou Beil military aircraft pursue them, forcing the pair to hide the plane and flee into the woods. Carlo reveals that the “secret weapon” they transport is himself—the heir to the Sou Beil throne. Wil explains that delivering Carlo to Roxche could end the long-standing war between the two nations. A Sou Beil scout discovers their location; Allison shoots him down but hesitates to kill. Wil takes the soldier’s rifle, insisting the mission’s success outweighs personal restraint. They seek shelter at an elderly woman’s cabin, and the woman recognizes Carlo as her grandson. She reveals herself as the former queen, provides supplies, and urges them to continue the journey without her. Sou Beil troops close in, and the group escapes through a hidden passage behind a waterfall. Soldiers capture the woman, but Allison and Wil flee with Carlo into the wilderness. Carlo resists running further, demanding they return to save his grandmother, directly challenging the mission’s priority.

Allison and Wil board a passenger train bound for the capital of the Sou Beil Federation,carrying a letter from a prisoner they met in the previous episode. During the journey, three aircraft bearing Roxche Allied Kingdom markings attack the train, strafing the cars and dropping explosives that damage the tracks. Allison, who possesses military pilot training, takes control of the train’s roof-mounted anti-aircraft gun and returns fire, while Wil observes the attackers’ insignia and notes their flight patterns. The attack forces the train to derail near Lake Lochans, leaving passengers injured and the train cars scattered along the shore. After the crash, Allison and Wil search the wreckage of one downed aircraft and confirm that its markings are authentic Roxche military insignia, but they find evidence—such as non-standard weapon configurations—that the planes were not from an official Roxche squadron. A Sou Beil military officer arrives with a detachment and reveals that the attack was a false flag operation orchestrated by a faction within the Roxche military aiming to provoke full-scale war. The officer, aware of Allison and Wil’s national origins from their travel documents, attempts to detain them as suspected spies. Allison and Wil flee into the surrounding forest, evading the initial search party and retaining the letter entrusted to them by a Sou Beil prisoner. Their original mission to deliver the letter to a contact in the capital now intersects with a broader conspiracy. Sou Beil forces intensify their search of the lakeside area, and the conspirators’ next move—another staged attack—threatens to ignite open conflict between the two nations. Allison and Wil commit to continuing their journey on foot, knowing that the information in their possession could expose the plot before it escalates.

Allison lands the plane near a small village to repair damage from the previous escape. A village boy named Carlo collapses from a recurring illness that requires a rare medicinal herb found only in a steep ravine. Allison volunteers to retrieve the herb despite warnings of predators and unstable ground. Wil follows her into the ravine,but a sudden rockslide separates them. Wil discovers an abandoned hunter’s shelter containing a journal with precise instructions for preparing the herb. Allison encounters a wolf guarding the herb’s location; she fires a flare to drive it away and extracts the plant. Carlo’s condition worsens before the medicine can be administered, and the village elder admits he does not know the correct preparation method. Wil retrieves the journal and follows its steps to produce the antidote. Carlo recovers fully, and the villagers reward Allison and Wil with fuel and supplies. As they depart, a military distress signal crackles over the radio, indicating fresh danger ahead.

Allison and Wil’s aircraft runs out of fuel over the Ixteen mountain range,forcing an emergency landing in a narrow valley. While scouting for supplies, they encounter a small military outpost of the Roxchean Commonwealth, which mistakes them for spies from the neighboring Sou Be-Agil Federation. Soldiers detain both and confiscate their belongings, including Allison’s pistol and Wil’s identification papers. During interrogation, Allison claims they are civilian surveyors, but the commanding officer remains skeptical after finding a map marked with strategic locations near the border. Wil attempts to explain their mission to locate the legendary lake of Muto, but the officer dismisses the story as a cover. The pair are locked in a storage shed under guard, with a warning that they will be transferred to central command in the morning. Inside the shed, Allison reproaches herself for the risky flight path that led to the fuel shortage, while Wil quietly examines the structure for possible escape routes. He notices a loose floorboard and a rusted ventilation grate that opens into a drainage ditch. After nightfall, they work the grate free and slip out under the cover of a passing patrol. They retrieve only their pistol and a compass from the unlocked equipment locker before fleeing into the forest. The sound of a search dog forces them to hide in a stream, losing their pursuers temporarily. As dawn breaks, they realize they are now deeper in the mountains with no clear direction to the next refueling point and the stolen map left behind. The episode closes with the distant roar of a Sou Be-Agil military aircraft overhead, indicating they have strayed into enemy airspace.

Allison and Wil board the transcontinental train to return to Roxche. During the journey,they meet a young girl named Fiona who carries a doll resembling Lillia. Allison notices a group of armed men moving through the cars and recognizes them as former soldiers from the previous war. The men take hostages and demand the train divert to Sou Beil territory. Allison hides Fiona and her doll in a luggage compartment before the soldiers search the train. Wil uses his knowledge of the train’s layout to move through ventilation shafts and reach the engine car. He disconnects the passenger cars from the locomotive, leaving the soldiers stranded with the engineer. Allison confronts the leader and reveals that his supposed allies in Sou Beil have already been arrested by Roxche forces. The soldiers surrender when they realize their escape route is blocked and reinforcements are not coming. After the incident, Fiona explains that she is traveling alone to find her mother, whom she believes is in Sou Beil. Allison promises to help her, recognizing the doll as the same one Lillia carries. The episode ends with the train resuming its course toward the border, where Roxche military officers await to take the prisoners into custody.

Allison and Benedict steal two planes from the Sous-Biel air force to transport Fiona to the capital of Ikstova,dragging a reluctant Wil along for the flight. During the journey, Fiona confesses to Benedict that she is not the true Princess Francesca; the real princess died in the fire that killed the royal family a decade earlier. In turn, Benedict admits that the credit for discovering the mural belongs to Allison and Wil, not to him. Allison performs aggressive takeoffs and acrobatics during the flight, leaving Wil airsick but successfully reaching their destination. They land directly in the midst of a political rally in the capital, scattering the crowd. Benedict introduces himself to the assembled citizens as the hero who found the wall painting and asks for permission to speak. Security Chief Warren and politician Owen Nicht observe from the stage, with Nicht agreeing to let Benedict address the crowd, hoping he will speak against independence. Benedict instead calls Fiona forward and announces her as Princess Francesca, the heir to the throne. Before Fiona can utter a word, Nicht interrupts, publicly accusing her of being an impostor. The episode closes with the two locked in a tense standoff as the crowd and authorities await the next move.

The episode begins with the group using alcohol to set fire to the last car of the train,detaching it to halt a pursuing military train. Allison spots an armored tank following them on parallel tracks across the river. Major Stork assembles an anti-tank rifle stored by the arms magnate, Gautier, and orders Wil to take the shot. Benedict shoots a hole in the train car to create a firing position. Wil lands a successful hit after several attempts, disabling the tank. Stork reveals to Wil that his true mission is to arrest Gautier for plotting to restart the war, and he admits to killing the conductor, Welch, to complete this objective. Gautier's bodyguard, Thomas, attacks Allison and the others in the dining car. Allison attempts to shoot him but misses repeatedly until Wil steadies her aim. Stork shoots Thomas in the shoulder before he can harm the group. The group finds Gautier dead in his suite, an apparent suicide that Stork views with suspicious calm. Wil grows increasingly doubtful of Stork's true intentions and motivations throughout the confrontation.

Allison and Wil remain imprisoned in a Roxchean military detention facility under suspicion of espionage for Sou Beil. Major Stork personally interrogates them,demanding they confess to their alleged betrayal. Wil refuses to admit to any crime, maintaining that their actions were intended to prevent a border incident. A young soldier named Fiona, assigned to guard the prisoners, recognizes Wil from their shared childhood in the same village. She privately confirms his identity and believes his claim of innocence. Fiona arranges a distraction and secretly provides Allison and Wil with the keys to their cell and a route to escape the compound. Under cover of night, the three move through the base until a patrol forces them to separate. Fiona stays behind to mislead the guards, while Allison and Wil flee into the forest. Major Stork discovers the escape and orders a search party to recapture them. The two fugitives reach a river and cross it, temporarily evading their pursuers. They now head toward the border, knowing Roxchean military units will continue hunting them.

The Allied Forces launch a full-scale invasion of the Bezel Kingdom,with Major General Gere commanding the advance. The Bezel military deploys its remaining units in a desperate defense around the royal capital. Allison and Wil take off in the ancient aircraft Vespa, carrying documents that prove the two nations share a common ancestry. Colonel Carr leads a separate Allied column toward the capital and privately questions the war’s legitimacy after seeing the evidence his son sent. Allison lands the Vespa on the palace grounds, and she and Wil present the historical records directly to the Bezel king. Faced with irrefutable proof that the conflict was built on fabricated enmity, the king orders an immediate ceasefire. General Gere receives the order on the battlefield and halts the Allied advance moments before a decisive clash. Soldiers from both armies stand down as the truth spreads through their ranks. The suspension of hostilities forces the political leadership on both sides to confront the consequences of the revealed history. With the war stopped, the narrative shifts to Lillia, who departs for the Royal Academy, setting up the next generation’s journey.

Lillia’s summer vacation begins as Treize arrives at her school by motorbike after a twenty-day journey from Ikstova. He brings her home,where her mother Allison changes their travel plans: instead of a mother-daughter trip to Lartika, Lillia will go with Treize. Lillia initially resists the change but agrees by the next morning. They travel by train accompanied by two royal guards, who later leave the pair alone. Upon arriving in Lartika, they check into a high-class hotel; Treize explains that a family friend owns the establishment. While sightseeing, they lose their way despite carrying a map. A local boy offers to guide them back for a fee, and they accept. When they reach the hotel, a policeman stops them and confiscates the payment, citing a town ordinance that prohibits such transactions, then takes the boy into custody. The following day, Lillia and Treize board a sightseeing plane piloted by Mateo, a retired military reconnaissance pilot. Meanwhile, Travas contacts Allison to warn that a conspiracy against Treize and his twin sister is underway, placing the two young travelers in imminent danger.

Lillia and Treize accept a delivery mission to transport a package to a woman named Fiona in a remote village. They fly the Beagle,but a man wearing a white mask attacks them mid-flight, damaging the engine and forcing them to crash-land. Separated during the crash, Lillia searches for Treize and instead encounters Carlo, a boy who is looking for his missing mother, Fiona. Treize pursues the white-faced man into the forest and discovers the man is a Roxchean soldier disguised as a Sou Beil officer. The soldier intends to assassinate Fiona and stage the incident to provoke a border war between the two nations. Treize attempts to stop him but is overpowered and left injured. Lillia and Carlo find Fiona hiding in a cabin, but the white-faced man arrives and takes them hostage. Treize recovers and confronts the soldier again, forcing him to flee without completing his mission. Lillia, Treize, Carlo, and Fiona reunite, and Carlo learns his mother had been protecting him from the political conspiracy. The group resolves to report the soldier’s actions to the authorities, but the white-faced man remains at large and continues to pose a threat to regional stability.

Lillia and Treize board a seaplane carrying a group of orphans for a charity trip. One hour into the flight,Treize realizes they have not reached their destination and should be over land rather than the open sea. He and Lillia go to the cockpit and find the crew parachuting out, abandoning the aircraft. Treize takes control of the seaplane and asks another orphan, Carlo, to help keep the children calm. When Treize attempts to change course toward the original destination, four fighter planes flank the seaplane. The fighters radio the seaplane, demanding that Lillia and Treize leave the aircraft or be shot down. Treize finds himself without options while the armed planes maintain their escort. Lillia makes a remark that gives Treize the idea to fight back by using the seaplane itself to knock the fighters down. On the ground, Travas monitors the situation from a concealed position and sends Allison to locate the missing seaplane, though he cannot give her a precise location. The episode ends with Treize preparing to engage the fighter planes directly.

Treize strikes one pursuing fighter with the seaplane’s wing,disabling it and activating its emergency beacon. The remaining three enemy fighters circle the damaged seaplane, giving Lillia and Treize time to delay them. Allison arrives in her fighter and shoots down the three hostile planes, eliminating the threat. With the attackers gone, the group faces the challenge of landing the damaged seaplane on the water. Treize doubts his ability to pilot the craft for a safe water landing. He manages to set the plane down, but it strikes a rock formation one hundred meters from the shore. The impact causes the seaplane to begin sinking in the shallow water. Allison circles overhead as the orphans and the young pilots find themselves stranded in the sinking wreckage. The immediate danger from the enemy fighters has passed, but survival now depends on reaching land before the plane submerges completely.

A sniper named Carr targets Lillia during her journey with Treize. Carr fires from a distant ridge,forcing the two to take cover in a forest. Treize assesses the shooter’s precision and deduces the attack is deliberate, not random banditry. Lillia recognizes Carr’s name from her mother Allison’s past war stories. Carr reveals himself to be a former soldier who served alongside Allison and Wil. He recounts his unrequited feelings for Allison and his bitterness over the peace that followed the war. A third party hired Carr to assassinate Lillia, exploiting his personal resentment. Lillia confronts Carr directly, refusing to flee and appealing to his memories of Allison’s character. Carr hesitates, recalling Allison’s unwavering commitment to protecting others. He lowers his rifle and allows Lillia and Treize to continue. The encounter reveals a hidden network of conspirators still active in the postwar landscape. As Lillia and Treize resume their journey, they realize the assassin’s employer remains unidentified and poses a continued threat.

Treize invites Lillia to Ikstova for the winter and plans to reveal his true identity to her. Allison takes a vacation from work to accompany Lillia on the journey. An avalanche blocks the road,and Allison joins other passengers in shoveling snow until a bulldozer clears the path. Wil Travas receives a report from his subordinate Axe about an anonymous account purchasing large quantities of expensive color film. Travas suspects a connection to a past incident and orders an investigation into the film company Lourie Production. Allison leaves the cabin to attend a New Year's Eve celebration hosted by Benedict and Fiona. Lillia stays behind with Treize, who prepares a home-cooked meal but loses his nerve to speak about his heritage as she enjoys the food. Elicia Lowry arrives at the party with her film crew under the pretense of recording the festivities. At midnight, as fireworks launch over the city, Lowry and her accomplices draw revolvers and take everyone at the party hostage.

Lillia and Treize land their damaged aircraft in a rural village after the Sou Beil military intercepts them. Colonel Carr orders aerial bombardment to force them out,unwilling to risk ground troops. The explosions destroy part of the village, prompting the two to move. Treize considers surrendering to stop the bloodshed, but Lillia insists they continue toward Ikstova. She argues that his capture would only prolong the conflict. They locate a military vehicle left by the attackers and drive away. Carr tightens the pursuit, vowing to recapture Treize at any cost. The villagers tend to their wounded, their trust in the military shaken. Lillia takes over the wheel while Treize checks their remaining fuel. Their route now leads through rugged terrain where air surveillance becomes less effective. Carr deploys ground units with orders to shoot if they resist capture.

Lillia and Treize arrive at a small border town seeking information about the Ikstova incident. Sou Beil soldiers detain them on suspicion of espionage. Colonel Carr,the local commander, interrogates Treize separately, attempting to extract details about his past with the Sou Beil military. Treize refuses to provide information, and Carr orders their transfer to a prison camp. A sympathetic soldier, Corporal Stork, secretly provides Lillia with a key and a map. Lillia and Treize escape through a drainage tunnel under the cover of night. They reach an airstrip where Stork has left a military aircraft ready for departure. Carr’s forces pursue them, and Treize takes control of the plane, using his prior flight training to evade anti-aircraft fire. The pair fly toward the royal capital of Sou Beil, where they hope to uncover the conspiracy behind the false accusations against Lillia’s father. Carr reports their escape to his superiors, who order him to erase all records of the incident, revealing a cover-up at higher levels that now directly threatens their investigation.

Lowry reveals her true identity as Claire and mistakes Lillia for Merielle,the royal family's daughter, taking her hostage. Out in the snow, Benedict and Fiona receive rescue from Travas and his team. The group returns to the cabin and disarms the bombs that Claire's team left behind. They discover Treize lying unconscious in the snow nearby. The group devises a plan to rescue Lillia and successfully captures Claire and her entire team without any injuries. Following the capture, Lillia, Treize, Allison, Benedict, Fiona, and Claire set out to find the treasure that Claire's father spoke about. Their search leads them to a hidden valley that functions as a secret shortcut to Sou Beil. The group realizes that if this passage had been discovered during the war, it could have changed the course of history. The revelation of this geographical secret shifts the context of the treasure hunt from personal gain to historical significance.

Carla arrives at the royal palace and reports to the king that the conspiracy to assassinate him has been set in motion. She names several high-ranking officers involved,prompting the king to order immediate arrests. Meanwhile, Lillia and Treize, still in the capital, receive word that the military has begun detaining suspects. Treize realizes their presence endangers the investigation and decides they must leave the city. Lillia hesitates, wanting to stay and fight, but Treize insists they lack the authority or evidence to intervene directly. They depart under cover of darkness, avoiding patrols that have started sealing off districts. On the outskirts, they encounter a group of soldiers loyal to the conspirators, who have set up a roadblock to prevent anyone from leaving with information. Treize creates a diversion by setting fire to a supply cart, allowing Lillia to slip past the distracted guards. As they flee into the forest, gunfire erupts behind them. They reach a small farmhouse where a contact provides horses and a map to a hidden border crossing. Lillia asks why the conspirators would risk open violence now, and Treize explains they are desperate to eliminate witnesses before the king’s forces can consolidate. At dawn, they hear distant explosions from the capital, signaling that the coup attempt has escalated into armed conflict. Lillia vows to return once they have secured outside help, and Treize warns that the success of their journey depends on reaching the neighboring kingdom before the conspirators seal all escape routes.

Princess Matilda of Sou Beil travels incognito on a reserved train guarded by Travas and his team. Allison and Lillia board a separate sightseeing train that conveniently breaks down,allowing them to transfer to Matilda's train when it stops nearby. Lillia confronts Treize about his presence, and Matilda intervenes, introducing herself as a trader named Hilda to maintain secrecy. During tea, Matilda notices Lillia's eye color matches Travas's and realizes Lillia does not know he is her father. A student passenger collapses from apparent poisoning, and a man accuses Travas's group, inciting other passengers. Allison deduces the man's movements were designed to create a disturbance. When the man takes Lillia hostage, Allison fires a gun near his head and negotiates Lillia's release. The man admits he was hired to cause chaos but denies poisoning the student; he and his female accomplice then convulse from poison they ingested themselves. Travas decides to separate the train cars at the next station to isolate the princess from the remaining passengers. He leaves Lillia, Treize, and the other civilians on the uncoupled section. Matilda's train continues but stops for a car placed on the tracks, and armed men immediately surround the train.

Lillia,Treize, and their companions arrive at the monument marking the site of the former war’s decisive battle. Federal Army soldiers already occupy the area and attempt to block entry, citing safety concerns. Treize confronts his father, General Schultz, who admits that the war’s conclusion was manipulated to consolidate political control over both nations. Lillia discovers sealed records inside the monument’s crypt that detail a massacre committed by her own grandfather’s unit. The military detachment receives orders to destroy the documents, prompting a shootout between the soldiers and the group. Using smoke grenades and the monument’s narrow corridors, the protagonists secure the evidence before the explosives detonate. General Schultz orders a retreat to avoid further exposure, leaving Treize to decide the next step. Treize resolves to make the documents public through a civilian radio station, fully aware that doing so will ruin his father’s career and trigger political upheaval. Lillia supports the decision, recognizing that concealing the truth would perpetuate the same cycle of deception. As they flee toward the nearest town, a broadcast van approaches, signaling the immediate chance to transmit the evidence before military reinforcements arrive.

After a woman lures Lillia away,Treize discovers that criminal mastermind Weasel, Prisoner #42, orchestrated the abduction to target him. Allison and Travas commandeer a biplane, the same model Allison once flew with Wil, and Travas addresses Allison by her first name for the first time in the series. Treize boards the speeding train alone, finds the emergency brake destroyed, and offers himself in exchange for Lillia. Confronting Weasel on the train roof, Treize reveals his identity as the prince of Ikstova, a fact Lillia accepts as the only explanation for the events. Allison flies the plane at dangerously low altitude through a forest to keep pace with the train, and Travas throws a rope ladder to the roof. Treize secures Lillia on the ladder, but Weasel grabs his leg as the train approaches a destroyed section of track. Treize releases the ladder, plunges with Weasel and the train into a ravine. Weeks later after spring break, Lillia returns to school to find Treize has transferred into her class, offering no explanation for his survival. At the school dance, Treize asks Lillia to dance, and she accepts, though their unresolved questions about his survival and true identity remain between them.