Sarah seeks help from Walker to get the mycosis cure and her team off of the island. Meanwhile Alan decides to destroy Mother but is interrupted by Peter leading to unexpected outcomes for everyone. Meanwhile, Sister Amy seeks to get her revenge on Anne.moreless
Alan finally finds a cure and is able to save Kyle. Meanwhile, Peter takes over the Abbey under his new name "Eli" and stops Kyle, Sarah and Soren from leaving the island. Alan and Julia find the Mother Tree.moreless
As the team prepares to evacuate the island, they learn that the Navy has already decided to make sure no one leaves the island by implementing a deadly Plan B. Alan's only hope is to find the cure. Meanwhile, Peter and Anne start to making plans for their future together.moreless
As Kyle gets worse, Soren takes the team to the Bleeding Tree. At the Abbey, Peter learns about Michael's breeding program, and Julia offers a new idea how to grant Amy immortality in exchange for Mother.moreless
Julia arrives at the Island along with Sergio where they meet Peter at the Abbey. Meanwhile, Alan, Kyle and Lt. Winger go into the woods searching for what may be a cure for the pathogen.moreless
Sister Amy makes a move with her own plans and deals with Michael. Meanwhile, the Coast Guard returns with news that the outbreak has spread and orders the CDC team to evacuate to another island but complications arise.moreless
Alan comes to, vaguely remembering what he did to Sarah who has to realize she suffered a tragic loss. Elsewhere, Walker decides to go to St. Germain after learning about Brother Michael.