Richard Cadogan is at loose ends in Oxford, very late at night. Charmed by the window display of an old-fashioned toyshop, he is worried to find the door unlocked; surely the owner should be alerted. And so Cadogan slips into the darkened store and up the narrow stairway to the apartment above.
But rather than a snoring toyman, he finds a very dead old lady, the marks of murder still livid on her neck. But when Cadogan returns with the coppers, the toyshop ... has disappeared.
This, it seems, is a matter for Gervase Fen.