Amelia wakes from a nightmare recalling images of herself and Jake hooked into the sleep clinic's machinery. She reassures Jake that it was just a dream.
Avram is locked in Room 53 of some building. Trevor phones Martin and says a vendor at the farmers' market saw a Hasidic man in his 40s being abducted yesterday.
Calvin tells Nicole Farington the sequence is nearly complete but still not consistently predictive. When it wraps back to 318, the beginning, they'll know it's ready.
Martin and Trevor learn that, although the vendor reported Avram's abduction, the police never showed up. Jake starts shaking violently, and Amelia says, "They're dying." They find Dr. McCormick writing in his journal, but shortly after Martin approaches him, he has a seizure and dies.
Trevor takes the kids while Martin waits for Detective Lange, and Jake shows Trevor the number 53. Martin runs into Dr. Nell Plimpton, McCormick's fellow sleep-center patient, and explains what happened. She says he made notes about his health in his journal, then mentions the study had seven people, now six. Martin recalls Guillermo mentioning the "nest of seven" before killing himself.
Martin tries to retrieve McCormick's journal from the morgue, but Farington's head thug already stole it and delivered it to Dr. Linus, the clinic's director.
Farington tells Calvin that Aster Corps' impending quarterly report will show a $40-billion loss. That's why she needs the sequence completed.
At the clinic, Calvin learns of McCormick's death. He wants to investigate, but Linus says he'll handle it.
Martin wants to get inside the clinic and find evidence. Trevor, afraid Aster Corps security will recognize Martin, volunteers to go instead. Posing as a friend of McCormick's with the same insomnia symptoms, Trevor takes a test to determine if he qualifies - and passes, thanks to remote help from Jake.
Calvin tells Farington he thinks Linus is hurting the subjects. She shrugs it off, reminding him that he kept Amelia prisoner for three years. Yes, he says, but she was safe. She says the sequence will let Aster Corps control the future, then threatens him, wondering what might happen to his brother William if Calvin is jailed.
Someone gives Avram a Hebrew bible with a passage marked from the Book of Isaiah that describes how the Lord will punish Leviathan, the swiftly moving serpent. Avram doesn't understand.
Calvin sneaks a look at McCormick's journal and brain scans and is appalled. He witnesses Nell having tremors like McCormick's.
Trevor slips out of his room and calls Martin, hanging up when a nurse catches him. Calvin intervenes, having figured out that Trevor's working with Martin, because only Jake could answer the test like that. Calvin creates a feedback loop to make it look like Trevor's still asleep. Meanwhile, Amelia urges Martin to save Trevor. He sneaks inside and finds his friend with Calvin.
Calvin explains about Linus' damaging experiments. Nell is already in distress, so Martin and Trevor rescue her while Calvin creates another loop, then returns to the lab. When Linus' team detects the loops, the facility is locked down, data is destroyed, and the staff departs before police arrive.
Martin and the kids take Nell to the hospital while Trevor fills in Detective Lange.
A Hasidic man apologizes to Avram for his treatment but says he can't let him go. "He will be here by tomorrow morning," he says, when everything will be explained. "He," who?
In the car, Jake slips a note into Martin's pocket. Amelia says, "It's happening." An SUV slams into the driver's side and knocks Martin out. Amelia and Jake are abducted.