"Inconceivable!"

Laurence Vining was not a particularly pleasant man. He was a genius, of course, and the police appreciated his help on the odd occasion where they found themselves out of their depth. In fact, just recently, Vining helped to put a murderer behind bars when the police were quite stumped, solving the mystery of the “Shop Murder”. He solves these cases with the help of his very own Watson, Dr. Benjamin Willing.

But despite Vining’s ingenuity, he’s a callous, cold-hearted man who manages to surround himself with enemies. Yet it’s something of a shock when Vining is murdered in a tube station under seemingly impossible circumstances! He gets into a lift by himself, and the operator sends him down— but at the lower level, when the doors are opened, Laurence Vining tumbles out of the lift dead— a knife plunged into his back. (The knife is a curious Oriental dagger, as a matter of course.)