Mark Lee

With cold weather approaching, Eve, Levi and Ty return to the fort, despite their near-death experience there, hoping to learn 10,000 B.C. survival skills; Gavin's attempts to spare Izzy pain threaten to do their relationship more harm than good.

With time running out before their window home closes, the survivors hatch a final escape attempt, but that plan is put into question when they receive a stark warning from Gavin that it will end in disaster, forcing Eve to make an impossible choice.

With news of one last sinkhole opening, Gavin, Izzy and Dr. Nathan race to Seattle to launch a final rescue effort before it's too late; Eve embarks on a perilous journey to send a young boy though a portal in order to save her family.

Desperate to reunite with her son, Eve follows a lead that brings her face to face with a ruthless prehistoric group; Gavin, Izzy and Ella question whether they're fit to survive in 10,000 B.C.; Josh and Riley wake up in an unfamiliar time.

Eve, Levi and the rest of the search party explore a mysterious fort that raises more questions than answers; with the help of a new ally, Gavin and Izzy embark on a dangerous and unauthorized mission to save their family despite government warnings.

When a stunning revelation puts Josh and Izzy's lives on the line, Eve and the other survivors desperately search for the young boy who holds the key to saving them; Gavin and Izzy must rely on a stranger if there is any hope to reunite their family.