The Man with a Cloak (1951)

In 1848, a young Frenchwoman, Madeline Minot, goes to New York City to see Thevenet, the grandfather of her fiance. Thevenet had been with Napoleon and may be sympathetic to the political aims of his grandson. She finds the old man in very bad spirits, living in a large house with a housekeeper and a butler who are just waiting for him to die (and perhaps helping him along a bit) so they can inherit his fortune. They see Madeline as a threat to their plans. She is aided in her dealings with these strange people by a mysterious man in a cloak.