Vaughan offers their captive a packet of blood, freshly drawn from his arm. The vampire smears it on the mirror and Angie notices a scar on his neck. Hearing his car alarm go off, Michael goes outside to find a cassette tape. It's from Jacob, electronic voice, he requests a meeting.
Kirsty meets Jacob in an empty building, he's hiding her from Michael and she finds the windows are covered over when she raises the blinds. She doesn't know who Michael is working for or why he tried to kill her, or why they are killing people.
Angie explains that fingerprints are like any other medium, they don't record so they can't get prints from the mirror the vampire touched. However, the scar on his neck dates from about 10 to 15 years ago, thyroid cancer. Harman is refusing to take his pain medication until the case is over but Angie reminds him that pain affects judgement and people who want quick answers cut corners.
Michael makes an excuse to Vaughan and goes to see Frances, he's sure Kirsty's being held against her will. She doesn't know what he is. Frances needs to know the truth if she's to help him. He replies that she'd have to see it for herself and he hopes she never does. Frances goes with Michael to Jacob's old office and they talk to his editor. Jacob hasn't been filing much the last six months, just using the facilities. He wiped the computer before he left. Michael looks up to find Vaughan standing in the doorway. He warns Frances to keep typing as if she works here. She tries to recover the deleted files. Vaughan is here because Jacob was researching cancer patients, thyroid cancer, and assumes Michael is here for the same reason. Frances astutely guesses Vaughan is 'the army guy' Michael had her research in the beginning. She manages to recover files and Michael says to keep a hold of them until he gets rid of Vaughan, whom he tells there are no files recoverable. Jacob must have gotten too close to them and they 'took' him. Vaughan asks if Frances is a friend, body language. Michael denies it.
The vampire talks to Harman about the environment and how they're trying to stop humans from becoming extinct. Harman turns the conversation around, saying the vampire had cancer and became one to save himself. The vampire knows Harman's sick and guesses that they drove Harman into the priesthood.
Kirsty finds Jacob sending an electronic message and comments that he doesn't smell at all. She asks how they get out of this and he asks if she trusts him. She doesn't answer. Jacob starts eying her neck so makes an excuse to go out. Michael and Vaughan search Jacob's apartment. Michael finds Kirsty's jacket. Vaughan finds a file on Michael but it's all old information, no address. Video tapes show destruction of rain forests around the world. If the vampire was an environmentalist, they might get a name. Angie gasses the room, paralyzing him. She takes blood but it is invisible.
Kirsty tries to hack Jacob's computer but can't get in. She explores the building instead and on the ground floor, finds the guard's station empty but a hat and jacket on the chair. On the security monitor, she sees a man sitting in a car, unmoving, in the parking lot. She goes to investigate, finding Jacob feeding. She runs but Jacob catches her. She wakes up and the same guard is with her but there's nothing on his neck and he has no memory of what happened. Jacob admits what he is and brings up Jack – Michael killed him.
Jacob repeats the same phrase they always use – no-one goes who doesn't want to go. Jack loved her, would have told her everything if he'd had the chance and then Kirsty would have joined him. He points out Michael was going to kill her for the same reason he killed Jack – they scare him. Michael and Kirsty can't tell the difference so are they really that different?
Angie's tests have turned up nothing useful. Michael finds a name for the vampire – Paul Hoyle – who got cancer from the Chernobyl clean-up. Michael meets Jacob and insists on proof that Kirsty's okay. Jacob dials and hands the phone to Michael. She knows everything, including what he did to Jack. She hangs up on him and Michael aims his gun at Jacob. If Jacob doesn't return or Michael doesn't co-operate, Kirsty dies. They want Robert March. Michael is puzzled, he's a pile of ashes, what do they want with him? They need someone to end the war, they've been watching Michael since the start. Kirsty does care for Michael or she wouldn't hate him so much. Michael can make her understand about Jack, maybe she'd even like him killing for her. Michael leaves.
Hoyle asks to speak to Harman alone, who asks why he crossed over. Security detail dismissed, they talk for 45 minutes. Vaughan reacts with anger and confusion and when Harman won't talk, he searches Harman's office when he's left. He finds the medication that Angie prescribed and confronts her, guessing the illness is terminal. Vaughan plays her the recording of the conversation. When confronted, Harman denies any wrongdoing. Picking up the word 'poison', Angie says that radiation can cause cancer, they should look at the nuclear industry to find out who he is.
Michael goes to the vault and looks up Robert's vault number. He opens one of the vaults, getting a canister. Michael takes the canister to Frances. She wants to know what it is and he won't tell her, asking her to help him. Frances wants to know what she's getting involved with, "I don't know what she's worth, I'm not in love with her!" She refuses and she doesn't want to see him again. She goes out to her car, in tears.
Kirsty asks what it feels like to change. He talks about how empowering it is not to have a reflection. She wants to come to the meeting, that's the arrangement with Michael. She's confused why Michael wants to save her when he tried to kill her. He explains that to Michael, if she's human he'll save her, if she's not, she dies. She asks if Jacob's killed and he admits it, saying it's a war and they're fighting for survival.
Angie and Harman find out about Hoyle and talk to his employer. The woman mentions Frances and when she arrives, they take her to the office. They've found the answer to the vampires plan – they intend to cause nuclear winter to blot out the sun. Explosion, asteroid strike, burning rain forests all do the job. The synthetic blood is part of it. They ask Frances where Michael is and what he's been asked to do. They realize Frances doesn't know the truth. They find a canister gone. Frances won't talk until they tell her the truth. They take her to Hoyle. Harman shoots him and he explodes, shattering the mirror. Frances believes.
Michael goes to the meeting with the canister, unknowing he is under surveillance from his own people. Vaughan has a sniper rifle but Angie tells him to hold. Harman arrives, explaining the plan. Jacob grabs Kirsty as a hostage. This plan is why they've been taking scientists for years. After assuming power, they exterminate us – the blood isn't an alternative, it's a substitute. When Jacob almost bites Kirsty, Michael lowers his gun and places the canister on the ground. Jacob empties it on the ground, cutting himself to drop blood on the ashes. Vaughan and Angie open fire and kill Jacob, who explodes. The blood regenerates the ashes… but it's Jack, not Robert.
Kirsty wanted him back so here he is. Seeing Vaughan, he grabs Kirsty as a shield. He kisses her cheek, hisses "Get a life" and jumps the railing. Vaughan's team try to arrest Michael but Harman stops them, Jack's not important – they've learned how they regenerate. Harman asks if Michael is in or out. Harman tells Kirsty it was good advice.
Jacob is placed in the vault. Angie stands and stares into space, Vaughan watches her then walks away. Harman starts taking his pills. Kirsty is held at the office and Michael comes to release her. She slaps him. Did he think it would teach him a lesson? He replies that he tried everything else. She storms out.
Jack finds Michael walking home and says he owes him one, and assures him he'll leave Kirsty alone. He says they should keep in touch. Michael can't pull the trigger a second time and Jack walks away.