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.

The Harrises return to 10,000 BC, determined to upload a virus that will stop all sinkholes, despite knowing that this will mean they will never get home again. An unlikely leader rallies the Clearing to face an oncoming prehistoric threat.

When a Survivor is murdered, Lucas and Sam lead a contentious investigation to find the killer. Gavin embarks on a mission to save Eve from the fateful vision he’s had of her death. Eve finds herself closer than ever to seeing it come true.

A ruthless enemy holds the Clearing captive, threatening to kill a beloved Survivor if their demands for an unexpected item aren't met. Gavin and Sam lead the rescue attempt, aided by an old friend whose return holds more questions than answers.

When the Clearing and Fort unite to celebrate the union of Ty and Paara, the invitation of a controversial guest threatens to upend the festivities. Lucas offers Veronica an unexpected strategy to unravel her captor's odd connection to 10,000 BC.

Eve and Gavin ally with James to infiltrate the Lazarus Building in hopes of saving Ty and stopping Kiera from destroying their only way home. When a deadly horde awakens beneath the Clearing, Veronica must save Ella before a lethal sting kills her.

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.