Her Private Secretary (1940)

When a charming young man arrives to serve as a private secretary for the eccentric Helene Kiepergass a, he quickly becomes entangled in a series of mysterious events in her house. Amidst the arrival of a suspicious "nephew" from Mexico and a house full of peculiar guests, a romance blossoms between the secretary and the lovely companion Mary. He eventually is able to unmask two confidence tricksters amidst the residents.