Cambridge, 1940. It is the first winter of the war, and snow is falling. When an evacuee drowns in the river, his body swept away, Detective Inspector Eden Brooke sets out to investigate what seems to be a deliberate attack. The following night, a local electronics factory is attacked, and an Irish republican slogan is left at the scene. The IRA are campaigning to win freedom for Ulster, but why has Cambridge been chosen as a target? And when Brooke learns that the drowned boy was part of the close-knit local Irish Catholic community, he begins to question whether there may be a connection between the boy's death and the attack at the factory. As more riddles come to light, can Brooke solve the mystery before a second attack claims a famous victim?