The Janus Murder Case (1984) is Colin Wilson’s fourteenth novel and the second, and last, in what had originally been a projected series of twelve police detective novels. Janus employs some elements of the police procedural genre, but these are largely subordinated to its psychological and philosophical aspects. Wilson took the basic plot of the novel from his play about multiple personality, Mysteries (related to, but not to be confused with, his nonfiction book Mysteries: An Investigation into the Occult, the Paranormal and the Supernatural (1978)). The play, begun in 1979, was never produced, but it was finally published in The Death of God and Other Plays (2008).
Tredell, Nicolas. "The Janus Murder Case". The Literary Encyclopedia. First published 24 October 2012
[https://www.litencyc.com/php/sworks.php?rec=true&UID=23975, accessed 17 September 2019.]