Anne Cossey has a recurring dream of an avenue that reminds her of Hobbema's painting of The Avenue at Middelharnis. Beyond that she knows nothing of the place, except that it terrifies her. There is a great deal in her past that she cannot remember. Who is her mother? Who was her father? Who is she?

Then, while she is on honeymoon in Spain, her mother 'commits suicide' in a manner that Anne is the first to recognize as murder. From then on the knots begin to tighten, for Anne is on the civilian payroll of Chief Superintendent Kenworthy, now in his closing years at the Yard, and her husband is a detective-sergeant in the squad of Kenworthy's old winger, Shiner Wright. She unearths various files in the archives that might refer to her mother's elusive past, but then finds herself one chilly dawn abducted under anaesthetic and coming to in the very avenue of her nightmare.

The action grows increasingly sinister, giving Kenworthy one of his most complex cases to date - and John Buxton Hilton the opportunity to introduce a few more to his gallery of memorable characters, including Swannee Foster, a criminal individualist, whom many at the Yard have agreed not to harness.