The Devil Bat - 1940

Dr. Carruther seeks revenge on his old employers for betraying him and becoming rich off a product he invented. To gain said revenge, he electrically enlarges bats and sends them out to kill his employers and their families. He trains the bats to hate the particular scent of a perfume and gets people try it on before they go outside. Only a reported pieces together what’s happening and gives the Dr. a scent of his own medicine. (I’m so sorry for that)