S2, EP8 "Episode Eight"
The survivors prepare for a final attack on the aliens that could change the entire course of recent events; Bill understands that humanity's survival depends on him.
S2, EP7 "Episode Seven"
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.
S2, EP6 "Episode Six"
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.
S2, EP5 "Episode Five"
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.
S2, EP4 "Episode Four"
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.
S2, EP3 "Episode Three"
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.
S2, EP1 "Episode One"
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.