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 cold weather approaching, Eve, Levi and Ty return to the mysterious fort, despite their near-death experience, 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.