With the survivors’ food supply dwindling, Eve and Ty venture into the forest on a risky hunting expedition only to face unexpected dangers that threaten their survival. As an unlikely rescue mission comes to fruition, Gavin must put his faith – and the fate of his family – in the hands of an old friend with whom he shares a complicated past.

With time running out before their window home closes, the survivors of the sinkhole hatch a final escape attempt. That plan, however, is put into question when they receive a stark warning from Gavin that their plan will end in disaster and forces 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 BC. Josh and Riley wake up in an unfamiliar time.

While Gavin enlists the help of his grandfather to guide him to his missing wife, Eve and Levi navigate a horrifying new reality. In 1988, Josh and Riley discover they’re being followed by a suspicious man who reveals information about the mystery behind the sinkholes.

When their plan to infiltrate the Building goes awry, Gavin finds himself face-to-face with its enigmatic leader. Eve, Levi, Sam and Izzy are forced to rely on a former adversary to lead a rescue attempt. In 1988, Josh and Riley enjoy some fun before a startling turn.

With Gavin on the verge of dying, Eve and her family make a desperate attempt to set things right … even as an unexpected twist threatens to tear them apart forever. Veronica reveals a secret that sends her relationship with Lucas into jeopardy.