Julia is an art restorer who is restoring a fifteenth-century painting. Her work on a Flemish painting reveals a hitherto undiscovered Latin phrase which translates as "Who killed the knight?". She goes to the art authorities she knows to find out what it might mean. Oddly, at the same time, a series of murders, including art experts, patrons and restorers has Julia scrambling to find out what is happening. She finds that the mystery of the painting is interwoven with the mystery of the deaths around her.