Iris Henley is at odds with her father because she refuses to marry Hugh Mountjoy, nephew of her Irish godfather. She is in love with the wild Lord Harry Norland, a friend of Hugh's brother, Arthur. Harry has joined the Invincibles, an Irish political secret society, which assassinates Arthur despite Harry's attempted warnings. Harry, saved from betrayal by Iris, vows revenge on his friend's murderer. Iris returns to England, breaking her journey to stay with Mrs Vimpany, wife of an unsuccessful, avaricious doctor. Mrs Vimpany has been secretly paid by Harry to keep a watch on Iris.