Return of the Ape Man (1944)

Professors Dexter and Gilmore have successfully reawakened a tramp who had been frozen for four months. This was a preliminary stage for a more ambitious attempt at bringing a prehistoric man back to life. After a lengthy search, the two researchers find a body frozen in a block of arctic. Back at the lab, they revive him but he is unable to communicate with them and quite violent.

He manages to escape his holding cell and kill a policeman on the street. Dexter decides he must replace part of his brain to make him more compliant and capable of talking. His first choice of a brain donor is the fiance of Gilmore's niece, Anne. This upsets Gilmore so much that he pulls a gun on Dexter, threatening to shoot if he continues. Dexter is so angry that he schemes to use Gilmore's brain instead. Once accomplished, the modified ape man escapes and heads to Gilmore's house.