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

An uneasy alliance forms over plans to free Gus and the other kids from captivity. Desperate for a breakthrough, Dr. Singh conducts a risky experiment.

The zoo turns into a battle zone when the rescue mission takes flight, with families coming together — and falling apart — during the chaos.

Gus and his cohorts set out for Alaska to reconnect with Birdie, who's working on a cure for the Sick. But first, they test their luck at an old casino.

After a doctor joins Gus and his crew, they seek a way to the coast and stumble upon a plane owned by a family in desperate need of medical attention.