Episode 4 begins with the return of Tetsuro Okino from his disciplinary leave, only to find the company in a state of tension. Arumi Nikaido had undertaken a risky nighttime operation to investigate a small giant beast, which violates the law. Kintaro Kataoka, the head of accounting, is furious and demands disciplinary action against her. However, Arumi and Koji Tajima, the company's director, take responsibility for the action and temporarily defuse the situation.

The team discusses the possibility of capturing a live giant beast for research purposes. Okino presents a cost estimate for a live capture trap, but Kataoka argues that they primarily need a boat and money. The company is already facing financial difficulties, and the loss of the boat has made the situation even worse.

Arumi visits Okino to talk about a small animal she saw, which has an injured eye. Okino recalls similar images from his first mission and shows them to her. The two discover that the animal is actually Arumi's lost dog, Shiro, who has mutated into a smaller giant beast. Arumi is determined to capture Shiro before he grows even larger.

The company struggles to secure a new boat that fits their budget. Just as things look bleak, they receive a call informing them that someone has lent them a boat for free, thanks to their new homepage. The team is overjoyed, and Okino receives some of the credit for this turn of events.

Arumi and Ginnosuke Muto set out to capture Shiro using the trap. However, they encounter another giant beast, and Muto is injured while confronting an intruder on the island. Okino insists on helping Arumi, even though he is still suspended. Kataoka lifts his suspension just in time, and Okino rushes to assist.

Okino and Arumi manage to neutralize the giant beast, and the trap sensor indicates that something has been captured. However, the episode ends on a cliffhanger, revealing that the poison gas concentration on the island has reached a dangerous level, putting everyone at risk.