Seven Keys to Baldpate (1917)

A writer bets a publisher friend that he can write a 10,000-word novel in 24 hours. The publisher takes the bet, and gives him the "only key" to his Baldpate Inn, which has been closed for the winter, so he can write in complete seclusion. Things start heating up, though, when a succession of people who also have keys to the inn begin showing up.