- This is the first (and only) two-part Whovians story - originally it was written as a single episode, but it was felt it worked better as a two-parter.

- Hannah Celyn Griffiths wrote the script on spec over Christmas 2015 because the characters and the storyline wouldn't leave her alone and sent it to the production team in early 2016. It was commissioned immediately. 

- These episodes are a co-production between Watchers Productions and Bleak Horizons Productions, the company founded by Rhys Jones whilst he was at university which made several short horror movies such as Legion (which was a clip during The Master Of Fear) and The Birthday Party (which was a clip at the start of Dinner With Monsters).

- The people on the missing posters that Jen passes early in the episode are executive producer Rhys Jones' dad and sister, and executive producer Terrance Edward's partner.