My Beloved Juan(1950)

Original title: Mi adorado Juan

The strange disappearance of the dogs of his neighbors leads Juan to investigate the case on his own. It ends up finding out that the author of the robberies is a young woman called Eloísa, the cocky daughter of a scientist who uses dogs to create an antidote against sleep. Juan and Eloísa fall in love, but he will ask her to leave her luxurious mansion to live only with his salary.