Luke Marks is the husband and cousin of Phoebe Marks, who, along with his wife, attempts to blackmail Lady Audley. Luke uses information Phoebe gives him concerning Lady Audley’s past to leverage Lady Audley for money in order to purchase and maintain his public house, the Castle Inn. Luke is described as brutal and ugly in both appearance and behavior. He selfishly desires increasing amounts money yet drinks away his funds and mismanages his public house. In order to stop the blackmailing—and simultaneously kill her other enemy, Robert Audley—Lady Audley sets fire to the Castle Inn. Luke is badly burned but does not die. Later, however, upon becoming deathly ill, Luke reveals to Robert that Lady Audley did not actually kill her first husband, George Talboys. George survived his fall down the well and, with Luke’s help, fled the country.