The Return of Stanley Atwell (1970)

Stanley Atwell, the presumed dead son and heir to Lord Atwell's title and fortune, unexpectedly returns to the family estate having escaped a decade of mysterious captivity. Atwell's shocking reappearance causes chaos as he finds his sister Beatrice fighting to claim his inheritance, whilst close friend Pamela manipulates his puzzling return, and a dark family secret, in a bid to seize control of the Atwell fortune.