Blagorodnaya semya Arden nahoditsya na grani razoreniya: otets semeystva ser Redzhinald v kotoryy raz zakladyvaet rodovoe pomeste Mortleyk-holl, poka ego syn Richard, igraya v karty, promatyvaet ostatki sostoyaniya, poetomu vsya nadezhda na yunuyu krasavitsu-doch Elis, kotoruyu rodstvenniki planiruyut udachno vydat zamuzh.
V eto slozhnoe dlya semi vremya v londonskom obschestve poyavlyaetsya bogatyy dzhentlmen Uolter Longklyuz, o proshlom kotorogo nikomu nichego neizvestno. Longklyuz bystro zavoevyvaet raspolozhenie Ardenov: rasplachivaetsya s kartochnymi dolgami Richarda i dazhe gotov zhenitsya na Elis.
No chto skryvaetsya v temnom proshlom Longlyuza i tak li beskorystny ego pomysly? Kakoe otnoshenie on imeet k zagadochnomu ubiystvu, proizoshedshemu v starinnom zamke Mortleyk-holl dvadtsat let nazad?
