A massive sinkhole opens and splits the Harris family in two, with Eve and Josh sent to a mysterious primeval world. Gavin discovers that the visions that have plagued him for years might hold the key to bringing them home.
With Josh's life on the line, Eve traverses the dangerous wilderness back to the clearing to save him. Gavin and Izzy work to prove survivors are alive inside the sinkhole as government agents track them.
With the food supply dwindling, Eve and Ty venture into the forest on a risky hunting expedition. 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.
The sight of a crashing plane spreads a wave of unexpected hope as the survivors search for its fallen pilot. Gavin and Izzy seek help from an unlikely source after the government permanently suspends their mission.
A 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 that they could cause unprecedented disaster.
With time running out before their window home closes, the survivors hatch a final escape attempt, but when they receive a stark warning from Gavin that it will end in disaster, Eve makes an impossible choice.
With cold weather approaching, Eve, Levi and Ty return to the fort, despite their near-death experience, hoping to learn 10,000 B.C. survival skills. Gavin's attempts to spare Izzy pain threatens their relationship.
When a stunning revelation puts Josh and Izzy's lives on the line, the survivors desperately search for the young boy who holds the key. Gavin and Izzy must rely on a stranger if there is any hope to reunite their family.
With news of one last sinkhole opening, Gavin, Izzy and Dr. Nathan race to launch a final rescue effort before it's too late; Eve embarks on a perilous journey to send a young boy through a portal in order to save her family.
