Pritchard and Duval join forces to track down a serial killer, and Alexa and Connor try to procure key technology from Lookinglass. Meanwhile, the bond between Mary and Pritchard has grown stronger, but Otto goes to great lengths to make sure Mary never leaves him, and Gracie suspects there is more to Pritchard than what he has told her.

Pritchard and Duval race against the clock to save Gracie from Connor and Otto's life-threatening experiment. But time is quickly running out for Pritchard, as well, since there is no tank in which he can regenerate. Meanwhile, Mary, with the help of Alexa, does everything she can to try and unlock the code to save Pritchard's life before it's too late, and Otto wrestles with his conscience and the decisions he's made that have changed lives forever.