Night of Death!(1980)

La Nuit de la mort

When she takes up her new post at an eerie convalescent home deep in the French countryside, nurse Martine soon discovers that several missing co-workers may have fallen prey to an unspeakable evil rumored to roam the hallways at night. But as Martine looks deeper into the mystery, she suspects the home's aged residents know more about the menace than they let on.