March 1941. Joseph Gunner is back on the streets of Glasgow after being wounded on the front lines in France. Keeping the pain in his leg at bay with the help of morphine, Gunner, a former detective, is hoping to keep his head down as the Luftwaffe begin bombing Glasgow. But when he runs into his old boss Drummond, he is persuaded to help examine a body found in the wreckage. When the body turns out to be that of a German, mutilated to disguise his identity, Gunner reluctantly agrees to investigate. As Gunner begins to hunt for the truth he runs into old flames, bitter enemies, before finding himself embroiled in a high-level conspiracy that reaches far beyond his hometown of Glasgow.