1949. An unsigned letter arrives on the desk of Chief Inspector Derry of the Canterbury police. Enclosed is a jade pendant, identical to the one that went missing from the body of Portia Blake, an actress murdered a decade previously. The case had been shut quickly at the time - the accused vagrant giving a written confession and sentenced to the gallows - but in the police's haste to close the inquiry, the necklace was never recovered. Until now. Inspector Madden is asked to investigate the letter's worrying claims by his old friend, and former Chief Inspector, Angus Sinclair, who fears the wrong man may have been hanged on his watch. But with a world war separating Madden from the murder, the truth will not come easy.