Part 4 opens with the case of Stella Nickell, a woman who loved her tropical fish but was known for having a contentious relationship with her husband. Stella ultimately poisoned her husband by lacing Excedrin capsules with cyanide. She was caught when a police investigation discovered traces of Algae Destroyer—a product used for cleaning fish tanks—in the poisoned pills. Detectives connected the Algae Destroyer to Stella’s aquarium and learned that she had mixed the aquarium solution in the same bowl that she later used to mix the Excedrin and cyanide.

Following this case study, the story resumes as Rich interrogates Mark at the police station. Despite the overwhelming evidence against him, Mark denies murdering Jess. Later, evidence reveals that Mark has an alibi for the time of Jess’s death. The narrative then switches to Emma’s perspective as she encounters news coverage announcing that Jess’s body has been found, wrapped in a rainbow quilt. Emma instantly recognizes the quilt as Jacob’s. She begins to panic, and the chapter shifts abruptly to Theo’s perspective as he reflects on painful childhood memories of growing up with Jacob.

One memory in particular stands out to Theo: he was seven years old and couldn’t wait to see the new Spy Kids movie in 3D.