Satan Met a Lady (1936)

Sardonic detective Shane, thrown out of one town for bringing trouble, heads for home and his ex-partner's detective agency. The business is in a sad way, and Shane, who has had the forethought to provide himself with a 250-dollar commission from an old lady on the train, is welcomed with open arms. When pretty Valerie Purvis walks in the next day willing to pay over the odds to put a tail on the man who did her wrong, Shane's way with the ladies looks like paying off yet again. But things start to go wrong when his partner is murdered, and Shane himself comes home to find his apartment wrecked by a gentlemanly crook who comes back to apologise -- and to tell him a fascinating fairy-story about the fabled Horn of Roland that looks like not being so mythical after all. Miss Purvis wants protection. The police want answers. And all sorts of people want the 'French horn'... but Shane is one jump ahead of everyone all the way. Well, almost.