The story of two boys living in Portsmouth at the time of the First World War.

Jimmy and Reg have no fathers, and help eke out their mothers' paltry wages by mudlarking - scavenging for coins in the black mud of Portsmouth harbour.

When they find a skull in the mud, they unleash a chain of events which end in the boys uncovering a terrible secret of murder, and being drafted into the army to stop them talking.