Three young women share a London flat. The first is a coolly efficient personal secretary; the second an artist. The third interrupts Hercule Poirot's breakfast of 'Brioche' and 'Chocolat' insisting she is a murderer – and then promptly disappears. Slowly, Poirot learns of the rumours surrounding the mysterious third girl, her family – and her disappearance. Yet hard evidence is needed before the great detective can pronounce her guilty, innocent or insane…