An experiment on a simpleton turns him into a genius. When he discovers what has been done to him he struggles with whether or not what was done to him was right.
| Actor | Role |
|---|---|
 Cliff RobertsonCharlie Gordon | Charlie Gordon |
 Claire BloomAlice Kinian | Alice Kinian |
 Lilia SkalaDr. Anna Straus | Dr. Anna Straus |
 Leon JanneyDr. Richard Nemur | Dr. Richard Nemur |
 Ruth WhiteMrs. Apple | Mrs. Apple |
 Dick Van PattenBert | Bert |
| EEdward McNallyGimpy | Gimpy |
 Barney MartinHank | Hank |
| WWilliam DwyerJoey | Joey |
| DDan MorganPaddy | Paddy |
| MMarianna CaseYoung Woman (uncredited) | Young Woman (uncredited) |
| LLeon CollinsTap Dancer (uncredited) | Tap Dancer (uncredited) |
| HHarry CooperConference Attendee (uncredited) | Conference Attendee (uncredited) |
| FFrank DolanEddie (uncredited) | Eddie (uncredited) |
 Randee Lynne JensenWoman (uncredited) | Woman (uncredited) |
 Ralph NelsonConvention Speaker (uncredited) | Convention Speaker (uncredited) |
| DDonald WarnockConference Attendee (uncredited) | Conference Attendee (uncredited) |