The original screenplay referred to the disappearance of a teenage girl, and the parents of the baby appear to have a tense relationship. While this didn't make the final cut, it does exist in the form of a prologue video that was released as a teaser, almost two years before the full release.
The missing teenager shown in the prologue is the parents' former babysitter, Alison Caperton. As part of building the back story, a series of websites, social media profiles and YouTube series were commissioned, with Emma Wicks playing the part of Alison. It would chronicle the former babysitter's spiral from confident young lady into depression and paranoia, prior to her disappearance.