 It is set in Watch Hill, Rhode Island.Pessl said in an interview, "I was working on my next adult novel, and I had this little germ of an idea about these five teenagers who used to be friends coming together in a sort of Agatha Christie-style, claustrophobic mansion type setting where they’re stuck.And at the time, I was very much interested in the brain and the consciousness and what’s real and what isn’t, so I definitely started going down this rabbit hole of trapping them and having them stuck in a way that went beyond anything Agatha Christie ever came up with."