Knock, Knock, Who's There?

An ordinary day - which turns to blackmail and murder. Classic crime from one of the greats of the Detection Club.

What seemed like an ordinary phone call in the middle of the afternoon suddenly plunges its recipient, Simon Crete, into a plot of blackmail and murder. 'Tell him it's no use. I haven't got it,' the mystery woman's voice cried desperately down the line. But who was she? And why was she ringing a man whom she had never seen?