When an old woman storms into the Rijks Museum demanding the return of her painting, archivist Ruth Braams cannot quell her curiosity. Together with Myles, her gay confidant, Ruth delves into the history of the piece of looted Nazi art and discovers an enigmatic picture with a disturbing wartime provenance. It also appears that the elderly Lydia is not the only claimant and, against strict bureau regulations, Ruth endeavours to help strengthen her case. Days later, Ruth begins to receive sinister anonymous threats, warning her to stay away from Lydia and the painting. When the door of her home, a houseboat on the Bloemgracht canal, is covered in graffiti and her gas supply tampered with, Ruth is convinced these are deterrents from the rival claimant. Our irrepressible and emotionally troubled heroine refuses to take them at face value and continues to strike up a friendship with the lonely old lady. But as the threats escalate, Ruth realises that there must be far more to the painting's popularity, and she enters into a series of increasingly lethal adventures as she investigates the painting's secret symbolism...