When a pack of venomous proto-mammals comes through an anomaly into a school during Saturday detention, the team must hurry to rescue the students and get the creatures back through the anomaly. Meanwhile, Abby fights to save the lives of the creatures in the Menagerie.
- Bad People Abuse Animals: Philip shows subtle signs of this with his plan to have the creatures killed. Despite making it out to be mercy and a necessary security precaution, Abby believes that he's just out to kill Rex because of what happened in the previous episode.
- Blackmail: Lester threatens to expose Phillip's treatment of the creatures to the public in order to dissuade him from having them killed.
- Call-Back: Lester references the Columbian Mammoth saving his life from a Future Predator as what convinced him to help Abby save the creatures.
- Death of a Child: In a series first, one of the students is attacked and killed by a Therocephalian.
- Disproportionate Retribution: Depending on how sympathetic you are towards them, Phillip's order for the creatures in the Menagerie to be euthanized can be seen as this. While it is true that Phillip nearly died when Rex triggered a lockdown, the original idea for the airtight lockdown was Phillip's, and he's ordering that all the creatures be killed for the ultimately harmless actions of one. Not to mention the irreparable damage this could've done to the timeline.
