Maud Silver, demure private eye, is on a train to London when a young woman in a state of shock bursts into her compartment. She is Lisle Jerningham, a newlywed with a fortune - which may be about to get her killed.

Lisle explains that she fled her home in a hurry after overhearing a sinister conversation. Her new husband's first wife died in an apparent accident, and the resultant infusion of cash saved his family home. Now, he's broke again - and she fears he is attempting to engineer a second convenient mishap.

Whether the widower is bent on a second murder or his young wife is being paranoid, no one is clear. But if Lisle is in danger, it is up to Miss Silver to find out.