The Dupayne, a small private museum on the edge of London's Hampstead Heath devoted to the interwar years 1919-39, is in turmoil. The trustees—the three children of the museum founder, old Max Dupayne—are bitterly at odds over whether it should be closed. Then one of them is brutally murdered, and what seemed to be no more than a family dispute erupts into horror. For even as Commander Adam Dalgiesh and his team investigate the first killing,...