The story begins, almost inconsequentially, when a strange girl encountering Con Gardiner in the street, asks him for the loan of a pound Gardiner is a solitary with no family, who leads a lonely existance in a one-room flat The girl, Charlotte Graves, aka Caro, has left her husband after a bitter quarrel and, significantly it transpires, he has been murdered a short while after - a event which involves the protagonists in a whirlpool of suspicion, tension and exciting suspense