Six months after Emily disappeared on an alien ship, the London survivors have set up a resistance base from which they plan to fight back; the aliens have since appeared and they look exactly like humans.

The episode was rated 7.31 from 534 votes.

After the devastating alien attack, disparate pockets of survivors emerge into a shattered world. They quickly realise they must put their differences aside if they are to stand any chance of survival. For they are not alone. Something sinister lurks in the shadows and whatever it is, it won't consider its victory complete until it has killed every last human. But who are these attackers and why are they hell-bent on destruction?

The episode was rated 7.32 from 1011 votes.

At the university, Sophia watches the videos recorded by Dylan, a young man they found dead, while Catherine focuses on the algorithms he left behind and which decipher the behavior of robots. Thanks to Bill's intervention, Isla manages to flee and join her family.

The episode was rated 7.33 from 402 votes.

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.

The episode was rated 7.34 from 470 votes.

Cracks start to show as the survivors find different ways to cope. Jonathan’s increasingly perturbed by Sacha’s strange behaviour. Emily proves to be an exciting conundrum for Bill. And Mokrani is horrified as his men delight in the opportunity to exact revenge.

The episode was rated 7.34 from 790 votes.

When astrophysicists detect a transmission from another galaxy, it is definitive proof of intelligent extra-terrestrial life. The world's population waits for further contact with baited breath. They do not have to wait long. Within days, mankind is all but wiped out; just pockets of humanity are left in an eerily deserted world.

The episode was rated 7.34 from 1316 votes.

Betrayed, Tom forges an unexpected alliance with Zoe. Confronted with the teenager, Bill must again answer for the consequences of his sacrifice. Zoe takes a drastic step to stop Adina's plan. From the alternate world, Catherine discovers that interstellar activity is badly affecting people. She sets out to find a solution, but is in serious danger.

The episode was rated 7.36 from 89 votes.

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 episode was rated 7.37 from 744 votes.

The survivors make some disarming discoveries not only about the aliens but also about themselves. Mokrani goes on the offensive, taking the fight to the aliens. Ash is forced to make the hardest decision of his life. And Chloe’s past catches up with her, threatening to rip apart the delicate semblance of normality she is so desperately clinging on to.

The episode was rated 7.39 from 843 votes.

After saving humanity, Bill Ward finds himself locked up in prison. Bitter, he will take a close interest in a new subject: many people around the world are victims of mysterious visions, including MI5 agent Zoe. Meanwhile, the discovery of a black hole prompts Catherine to investigate this global phenomenon.

The episode was rated 7.44 from 146 votes.

Catherine, Sophia, Zoe and the other survivors, finally reunited, prepare for the ultimate attack. But it is Bill who is the only one to hold the fate of humanity in his hands, provided he is helped by Isla.

The episode was rated 7.54 from 401 votes.

Martha unwittingly unleashes a fatal gunfight resulting in severe damage. In the alternate world, Catherine and Sam arrive at their destination, but encounter some unforeseen events. Bill then tries to contact Catherine, but when he can't reach her, he turns to a drastic solution.

The episode was rated 7.59 from 63 votes.

Bill investigates more of Catherine's findings and thwarts the aliens' deadly plans, but the group finds themselves in danger once again. Meanwhile, a run-in with the aliens ends tragically. Catherine secretly hatches a plan against her captors, but will she abandon Sam?

The episode was rated 7.60 from 57 votes.

Emily agrees to help Bill test her for the virus, but soon experiences serious side effects. Sacha, who has secretly followed the group to stay close to Emily, tries to remove her from the group. For their part, Catherine, Sophia and Nathan set out again in search of Bill Ward.

The episode was rated 7.60 from 386 votes.

Astronauts Juliet Arquette and Richard Gallagher witness Catherine's theories in space as Adina plots revenge against humanity. Mourning over the death of her sister, Catherine decides to research the phenomenon with the help of Johannes. An unexpected encounter prompts Kariem to continue her investigation of global psychosis. Faced with the damage caused by Adina's latest attacks, Zoe decides to turn to Bill to thwart the alien's plans.

The episode was rated 7.64 from 129 votes.