The alien's connection to certain survivors raises difficult questions. Bill makes a startling discovery. Sacha's behaviour is increasingly erratic. And Tom's birthday proves cause for celebration. But at what cost?

The epic series finale sees the survivors attempt to turn the tables on their aggressors once and for all. Mokrani and Catherine prepare for the fight of their lives. Emily seeks answers, at any cost. And Sacha's visions continue, giving a confounding glimpse of the future…