‘Black Mirror’: Kate Mara and Josh Hartnett Break Down That Shocking ‘Beyond the Sea’ Twist

Plus: Hartnett imagines what happens after the credits for Season 6, Episode 3 roll

Note: The following Kate Mara and Josh Hartnett interview discusses major spoilers for “Black Mirror” Season 6, Episode 3: “Beyond the Sea.”

Season 6 of “Black Mirror” introduces an alternative 1969 in “Beyond the Sea,” in which two astronauts, Cliff (Aaron Paul) and David (Josh Hartnett), quite literally experience the best of both worlds by spending time with their families on Earth in a replica of their likeness while their bodies remain aboard a multi-year space mission.

Although both men spend limited time together on the mission, when a cult leader kills David’s family and burns his replica, David has no choice but to spend all his time alone on the spacecraft. After Cliff begins to worry that David might not survive in his isolation, Cliff’s wife Lana (Kate Mara) suggests that David could use Cliff’s replica for a break appear in Cliff’s likeness to visit their picturesque home and the forest surrounding it.

“It’s exploring how isolation affects us on such a deep level, and how human connection is vital to our existence, happiness and health,” Mara told TheWrap. “That’s really what a lot of this episode is about… That’s why I wanted to be a part of it.”

All is well with David’s trips down to Earth as he works on a painting of Cliff and Lana’s home, though things begin to take a turn when David (in Cliff’s replica) begins hitting on Lana. In space, Cliff becomes suspicious of David’s intentions and forbids David from using his replica again — leading David to return to Earth in Cliff’s replica once more to commit a violent act against Lana and Cliff’s son to level the playing field.

“David has gone through an extraordinary trauma: he’s isolated as can be, literally in space, without anyone to speak to, except for a guy who is reticent and won’t speak with him about anything meaningful,” Hartnett said. “Beyond any expectations that he’s ever had, he finds that little glimmer of hope, and that little possibility of love and connection with Lana’s character, and to have that taken away, again, to endure that trauma again, would be too much. So he does something awful, and thereby creating a potential for connection between him and Cliff.”

By the end of the episode, Cliff returns to space, with his wife and child deceased, finding himself in the exact state of grief and isolation David felt several months before — though knowing Cliff must spend time with the man who decimated his family adds another level of twisted complexity.

As David motions for Cliff to take a seat at the table, Hartnett notes that the installment’s conclusion leaves Cliff with a choice for how the rest of their mission — and their lives — will continue.

“Does he sit down and join David and their mutual isolation and mutual grief and find a companionship, or do they both die up there?” Hartnett said. “It’s not gonna be easy for Cliff to come back to Earth. Everybody thinks he killed his wife — it’s so horrible.”

“Black Mirror” Season 6 is now streaming on Netflix.