When Terra Nova comes under attack from a legion of Pterosaurs, Jim and Taylor must find a way to save the colony before it's completely overtaken. Elisabeth discovers a former flame is also living in Terra Nova and may have been responsible for her recruitment. Syke tries to make Josh feel at home and Reynolds get protective of Maddy.

When an orphaned "Sixer" girl comes to Terra Nova seeking asylum, Jim and Shannon are at odds if they can trust her; Mira plots to reclaim a valued possession; Taylor begins to suspect there is a traitor in his midst and Reynolds admits his feelings for Maddy.