Music:
- God's Gonna Cut You Down, by Detroit Social Club, B-side from the single Prophecy (2010)
- Hungry Like the Wolf, by Duran Duran, from the album Rio (1982)
- History Repeating, by Propellerheads featuring Shirley Bassey, from the album Decksanddrumsandrockandroll (1997)
The scene in which the recovered Herrick (Jason Watkins) is trying to decide whether to kill Nina (Sinéad Keenan) appears to be taken almost verbatim from a similar scene in Alan Moore's comic Marvelman (later retitled Miracleman). This is perhaps unsurprising, given that writer and showrunner Toby Whithouse has previously expressed admiration for Moore's work when interviewed.