Jamie Vance, a Presbyterian married to a Catholic girl, plays a leading part in Donegal Unionism. His fiercest enemy is Diamuid O'Mara, a hard-bitten IRA fighter. The novel details assassination, murder, bombings, arson, and conspiracies in Ireland and England. Amid this disorder, the strained relationship between Jamie and his wife, Caitlin, and his obsession with an Anglo-Irishwoman is played out. Diarmuid develops a passionate relationship with a young Dublin girl and then a tough fellow IRA activist, Mire. During World War II, the two strands of Unionism and Republicanism clash head-on in a deadly struggle and reach an explosive climax in the Fermanagh Lakelands over a critically important Allied base in the forefront of the war against Nazi control of the Atlantic.