The team races to stop the hybrids from breaching the barrier wall by shutting down the last beacon that draws them in.
After the team’s plane suffers a catastrophic accident in the hybrid zone, Dariela and Tessa set out on a rescue mission to save them.
Clem manages to revive the team, but they’re trapped on the airstrip in Seoul amidst a cloud of spores. As they struggle to survive, Clem goes into labor and one team member will have to make the ultimate sacrifice to save the others.
After Jackson attacks Abigail, the team rushes to save her as her life hangs in the balance.
With the aid of a captive Shepherd, Jamie and the others trace Mitch–now Mr. Duncan–to Copenhagen. Meanwhile, Jackson escapes his captivity and goes after Abigail, while Logan finds a hybrid nest in Seoul.
While Logan tries to determine how the Black Forest hikers died, the jet suffers a series of malfunctions. Meanwhile, Abigail taunts Jackson in an attempt to get him to use his animal control powers and provide her with the missing piece of the puzzle.
After rescuing Isaac and the other children, the team travels to Peru to find the first of the three remaining hybrids and meet a familiar face. Meanwhile, Abe and Dariela try to work out their marital difficulties, and complications arise with Clem’s baby.
Mitch rescues Clementine, while Abe discovers that a combination of the baby’s DNA and the hybrids’ spinal fluid could provide a cure to the TX sterility. Meanwhile, Jamie and Logan learn about Abigail’s mysterious partner, Mr. Duncan, and try to identify him.
While Jamie’s under arrest, she manages to manipulate Mitch and Logan into helping her hunt Shepherds, members of a secretive group responsible for sterilizing humans.