At 1.20 a.m. on 24 March 1922, five men, four dressed in British police uniforms, broke into the North Belfast house of Owen McMahon, a well-known Catholic publican. They fatally shot McMahon, four of his sons and Eddie McKinney, an employee of the family. Nobody was ever charged for these ruthless and cold-blooded murders. In retaliation for these and other Belfast murders, the IRA assassinated the former head of the British Army, Field Marshal Sir Henry Wilson, and a subsequent British ultimatum to the Irish government sparked the first salvos of the Irish Civil War days later. The reluctance of the unionist Belfast government to pursue loyalist killers drove the rift between Northern Ireland's two main communities even deeper, laying the foundations for the Troubles at the end of the twentieth century. Over 100 years later, Edward Burke has expertly uncovered the identity of the McMahons' likely murderer. This is a riveting cold-case investigation that invokes the smoke-filled streets of Belfast during the cataclysmic violence of 1920- 22, and explores how the ramifications of the McMahon killings are still being felt to this day.