Devlin the Barber by B. L. Farjeon

Classic Victorian paranormal novel!
Lizzie Melladew is murdered and her twin sister disappears, they are led to Fanny Lemon whose husband is ailing from a mysterious and seemingly demoniac illness. And who talks in his sleep of Lizzie's murder – hours before it happened! And to add to the eerie situation, his sickness seemed to coincide with the arrival of a fascinating new boarder – Mr. Devlin.
Devlin is able to describe Lizzie's parting with her parents prior to the murder, something he had no way of knowing. Who is Devlin and what are these powers he seems to have?