Fingers At The Window (1942)

Starring Lew Ayres, Laraine Day, Basil Rathbone, Walter Kingsford, Miles Mander
Directed by Charles Lederer
(actor & director credits courtesy IMDB.com)

An out-of-work actor comes to the rescue of a lady stalked by a man with an ax, the latest would-be victim in a series of murders by different killers, and he tries to determine how they're connected.  

MGM delivers a fun and entertaining thriller with many talented thespians in the cast, highlighted by Ayres' charming and selfless hero, Day's slightly daffy leading lady, and Rathbone's sinister villain. Although the subject matter is rather grisly and disturbing, with ax murders and the exploitation of the mentally ill central to the screenplay, the film does not come of as such with plenty of light hearted moments balancing out the grim ones.  This is a fun and diverting picture.

Donovan's Brain (1953)

Starring Lew Ayres, Gene Evans, Nancy Davis, Steve Brodie, Tom Powers
Directed by Felix Feist
(actor & director credits courtesy IMDB.com)

After failing to save a wealthy man's life, a scientist steals his brain for further research, unsuspecting of the power it will soon wield over him.

One of several film adaptations of Hollywood screenwriter Curt Siodmak's novel of the same name, this is probably the best of the bunch, featuring a strong performance by Ayres as the kindly scientist whose mind is taken over by the brain and transformed into a ruthless industrialist.  Gene Evans and future First Lady Nancy Davis (Reagan) are good in supporting roles, and Feist and crew cleverly expand the brain's size when it's advancing its evil agenda, and shrink it back down when dormant, accompanied by appropriate sound effects.