Conversation so far:
Who/what is Gef for Harry Price?
Gef, Talking Mongoose or the Dalby Spook, was the name given to an allegedly talking mongoose which was claimed to inhabit a farmhouse owned by the Irving family.
Are there any other interesting aspects about Gef the talking Mongoose?
The Irvings' claims gained the attention of parapsychologists and ghost hunters, such as Harry Price, Hereward Carrington, and Nandor Fodor.
What was the case the Gef for Harry Price?
Price and Richard Lambert went to the Isle of Man to investigate the alleged case of Gef the talking mongoose and produced the book The Haunting of Cashen's Gap (1936).

Question: What did they conclude?
Self-contained rewrite: What did Harry Price and Richard Lambert conclude about the Gef case?