Maddy starts interning for the colony's greatest scientist, and her life is put in danger when she discovers a terrible secret. Meanwhile, Josh makes a deal with the devil in order to solidify his plan to bring his girlfriend from the future to Terra Nova.

As Taylor searches for the "Sixer" mole within Terra Nova, Jim stumbles onto an old murder, for which Taylor is the prime suspect.

Taylor and Mira square-off in the jungle where he learns more about her plans and about his son. But then they both face a pre-historic enemy they must conquer together. Meanwhile, the "Sixer" mole scrambles to cover its tracks as Terra Nova goes on lockdown and Jim closes in. Also, Zoe faces a difficult decision as the Ankylosaur she has been caring for grows rapidly.