As people across the globe are experiencing hallucinations, MI5 agent Zoe contacts Bill for answers; Catherine Durand detects unusual black hole activity.
As Adina starts the next stage of her plan, astronauts Juliet and Richard see warning signs in space; uncovering Adina's sinister mission.
With Richard's help, Catherine discovers she can travel to another world; a new revelation puts Martha's loyalties to the test; Zoe breaks Bill out of prison.
A deadly face-off leads to a life-threatening moment; Catherine and Sam seek help for his parents.
Bill's latest discovery is put in jeopardy, even as trouble brews with the human aliens; Catherine must decide where her loyalties lie.
Adina's plan for world destruction reaching completion; those in the alternate world are under attack.
With Adina's plan in motion, the world's last hope is for Bill to make one more journey, risking his own life in search of Catherine's help.
Six months after Emily disappeared onto an alien ship, the London survivors have set up a resistance base from which they plan to fight back; the aliens disappeared and they look like humans.
As Emily grows concerned by her recollections of time spent with the aliens, Bill is also perturbed by the similarities between Emily and the aliens; Zoe encourages a reluctant Bill to use these similarities to their advantage.
Bill secretly injects Emily with a biological weapon he hopes to use on the aliens; when she becomes sick, some of the survivors head out to find insulin in order to treat her; the resistance base is attacked and the survivors are forced to flee.
Catherine, Nathan and Sophia find an ally to help them get to London, but their trip is not without danger; as Adina, Reuben and the other aliens search to find Bill Ward, they realize that they're not immune from danger themselves.
Catherine makes new discoveries about the aliens as she, Nathan and Sophia continue their search for Bill in London; Bill explains his plan to infect the aliens with a virus.
Catherine focuses on computer algorithms left by a human survivor which explain the behavior of the alien creatures and makes a startling discovery about how the aliens traveled to earth.
Catherine, Sophia and Nathan are finally united with Bill and the group in London; as Catherine and Bill share their knowledge of the aliens they make a devastating realization about how the alien race came into existence in the first place.
Astronomers detect a transmission from another galaxy, and the people of Earth await further contact with baited breaths.
After the devastating alien attack, disparate pockets of survivors emerge into a shattered world.
Survivors hide in the hospital, but their enemy is close.
The survivors make alarming discoveries not only about the aliens but also about themselves.
Cracks start to show as the survivors find different ways to cope.
The alien's connection to certain survivors raises difficult questions.
Tragedy strikes, altering the course of the future forever.