Paul Ravenel is brought up abroad in mysterious circumstances. Upon his return to England he learns that his father was disgraced as an army officer in India and assumed French nationality. Determined to expiate his father's crime, Paul joins the French legions. Sent to Morocco, he falls in love with Marguerite, and stays with her rather than join his unit during a revolt in Fez. He thus disgraces himself, as did his father. His comrades believe him dead in the massacre of Europeans that occurred, but his friend Gerard then discovers the truth. He disappears and by a series of secret ventures gradually climbs the winding stair to vindicate both his love and his honour.