Zoe settles her team into their new digs. Tom spots something odd about his girlfriend and battle lines begin to blur.

The human cost of the war is something the show has always been good at and arguably never better than it is in this episode. The entire cast are haunted and haunting this season, ghosts in their old lives, and Tom has been one of the forgotten victims up to now. Emily’s softly spoken, good-hearted brother bonded hard with Bill in the old timeline and when he spots that Bill has been broken out of prison, makes contact with members of Emily’s off the books team of ragtag terrified civilians. He doesn’t know it of course; he thinks he’s just talking to survivors but survivors and soldiers are the same thing in this war.

This episode collapses without Ty Tennant, his performance central in every way. His growing confusion and terror around Bill are the emotional heart and Tennant and Byrne are great in the scenes they share. Tom isn’t angry, he’s just deeply confused and traumatised and, like everyone else, haunted by the bigger picture of the war. Bill, for his part, is burnt up with guilt about killing Emily and honestly terrified of facing her brother. Their scenes, as well as the Spooks-esque counter intelligence operation Zoe and co are running around London, are great fun as well as being abjectly terrifying. The war didn’t stop, it’s just changed shape.

The dramatic heart of the episode explores that in two different ways. The first is the slow burn reveal that the black hole is making it impossible to live outside for longer than 45 minutes or so in the original timeline, which the aliens are taking advantage of. The second is the revelation that Tom’s girlfriend, in the new timeline, is an alien too.

This is where things get nasty and blackly funny. Pearl Chanda’s Zoe is a stone-cold, calm presence running a team of panicky newbies and her laconic tone is perfect. It cuts through and accentuates the sheer terror everyone feels in this plot and which becomes the core of the episode as it concludes. Tom being worked from both sides, Zoe torturing her suspect and Bill quietly aware that the only person who knows he doesn’t have a plan is himself. Tom’s choices all the way through are vastly contradictory and also make total sense and it’s a pleasure to see a show like this embrace untidy human complexity with such gusto.

Verdict: Grim as ever but wider in scope than before, this is another great episode of a criminally overlooked and profoundly confident show. 9/10

Alasdair Stuart