Mark Lee

Gavin enlists his grandfather's help 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 man who reveals information about the mystery behind the sinkholes.

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.

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 plans to infiltrate the building go awry, Gavin comes 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; Josh and Riley enjoy some fun before a startling turn.

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.