Captain Gabriel Lacey travels with Lady Breckenridge to his boyhood home in northern Norfolk only to discover mysterious happenings in and around the Lacey estate. A young woman, cousin of an old friend, has gone missing, strange objects appear in Lacey's ruined house, and the dark windmills on the marshes keep pulling Lacey to them. The underworld criminal, James Denis, uses Lacey's visit to Norfolk as an opportunity to have Lacey deliver a message...