A car speeds down a road between miles of marshes and estuary flats, its passenger a young woman named Agnes—hands bloodied, numbed with fear, her world turned upside down.

Meanwhile, the news of a girl found dead on the marsh is spreading round the local area, panic following in its wake. A masterpiece of suspense, Mary Kelly's 1962 novel follows Agnes as she casts her mind back through the past few days to find the links between her husband, his friends, a mysterious stranger new to the village, and a case of unexplained death.