The episode begins with Tsugaru and Shizuku accidentally misplacing Aya's head and replacing it with a parrot. This mishap sets the tone for the chaotic events that follow.

Next, the viewer is introduced to the iconic characters Sherlock Holmes and Arsène Lupin. Lupin, disguised as Holmes, meets the real Holmes and reveals his mastery of disguise and lock-picking. Watson is briefly confused by Lupin's remark about the security of Fogg's villa, but Lupin quickly steers the conversation elsewhere.

Mycroft Holmes makes a brief appearance and recognizes Lupin's disguise by his fingernails. Nevertheless, Lupin proceeds with his plans to steal the Penultimate Night and enlists the help of Erik, who can blend into crowds without a disguise.

Tsugaru, Shizuku, and Aya accidentally cross paths with Lupin and Erik, leading to an intense fight scene. They manage to inform Tsugaru about Lupin's true nature.

Inspector Ganimard, Lupin's archenemy, appears and further complicates the heist scenario. The night begins with the detectives taking their positions in the chamber for additional crimes, while the trio of Aya, Shizuku, and Tsugaru is excluded.

The appearance of an intruder triggers a red alert, but Holmes realizes it's a move by Lupin. He locks the doors and traps everyone inside as water begins to flood the chamber. Lupin has effortlessly lured his prey into the trap, and the characters engage in a race against time to escape the flooding.