SPOILER ALERT!! - The group convenes in the ruined Lab. With a new strain of the virus loose, the Lab's work to find a vaccine is more important than ever. Unable to find any signs of Whittaker (Nicholas Gleaves), Abby(Julie Graham) agrees to provide whatever samples are needed to create a cure. Al (Phillip Rhys), believing that he has nothing left to lose, volunteers himself to test the vaccine. Meanwhile, Whittaker, surviving off the serum he gleaned from Abby (in an earlier episode), continues to hamper the group's plans with lies and deceptions, leading them to the abandoned airbase for a final showdown with the mysterious Landry (Patrick Malahide). Series finale airs Tuesday, April 27th @ 10:00 p.m. EST/PST on BBC America.