Gus follows a reluctant Big Man into the unknown. Dr. Singh discovers what it will cost to save Rani. Aimee finds a new beginning after the world ends.

Eager to send Gus on his way, Big Man figures out how to hide him in plain sight. The Singhs attend a neighborhood party that takes an ominous turn.

Gus lands under the protection of some new friends as Big Man's past catches up to him. Dr. Singh fears a nosy neighbor will unearth Rani's secret.

Gus and Big Man pick up a traveling companion who suggests a perilous shortcut. Aimee's sanctuary comes under threat. Time's running out for the Singhs.

In a moment of desperation, Dr. Singh makes a bold promise. A lost memento makes for a bumpy ride to Colorado. The Last Men close in on the Preserve.

Gus's quest to find Birdie and uncover more about her connection to his father leaves him questioning everything he's ever known.

His world shaken, Gus runs off and makes a rash decision. Big Man comes to grips with long-ago mistakes. Aimee makes a last stand against General Abbot.