Quoting from a "teaser" on the flyleaf:

The well-known authority on criminology, Dennis Holt, inherited a house in a remote village, the sort of place in which, to quote himself, “nothing ever happens.” One night at fifty-three minutes past eleven , his attention was attracted by a peremptory tapping on the window pane. A moment later, the lower sash was slowly pushed up and a young girl appeared.

“Let me in!” she whispered. “Please—I have hurt myself.”

That was the beginning of a bewildering series of happenings in the life of Dennis Holt. Suddenly he found himself precipitated into the midst of a bewildering mystery, which at one time seemed to threaten even his own liberty. Patiently piecing together the ascertained facts, Holt eventually presented a remarkable reconstruction of what had taken place on that dramatic night.