.....is the thickest London particular in half a century and it complicates the attack on an unknown man so that the Yard's Macdonald has a large assortment of leads to run down. A psychiatrist and his young secretary; an engineer; the young man's identity -- all lead back into an old disappearance case and an unsolved wartime riddle. Commonsense versus psychic bids and a fog to hinder wraps it up.