Which film is about a man who goes from retardation to genius and back again?

In the 1968 film "Charly", it is about a man who goes from retardation to genius and back again. "Charly" is an American drama that was directed and produced by Ralph Nelson. It was written by Stirling Silliphant and was based on 'Flowers for Algernon', a science fiction short story (1958) and subsequent novel (1966) by Daniel Keyes.

The film stars Cliff Robertson as Charly Gordon, an intellectually disabled adult who is selected by two doctors to undergo a surgical procedure that triples his IQ. It is the same results which happened to Algernon, a laboratory mouse who also underwent the same procedure as Charly. Other roles are played by Claire Bloom as Alice Kinnian, Lilia Skala as Dr. Anna Straus, Leon Janney as Dr. Richard Nemur, Ruth White as Mrs. Apple, and Dick Van Patten as Bert.

In the film, Charly (Robertson), who has an IQ of 69, is constantly derided by his boss and fellow employees at the bakery where he works. His efforts to read and write prove fruitless. But when Dr. Straus offers Charly an opportunity to participate in a radical medical experiment, he becomes a certified genius. The newly educated Charly develops feelings for his teacher, Alice Kinian (Bloom). Their happiness is threatened by unforeseen complications regarding Charly's mental health.

"Charly" received many positive reviews from critics and was a commercial success at the box office in North America. On a budget of $2,225,000 US dollars, the film grossed $8,500,000 US dollars.