When brain surgery makes a mouse named Algernon into a genius, dull-witted Charlie Gordon, a mentally disabled man, wonders if it might also work for him. In poignant diary entries, Charlie tells how a brain operation increases his IQ and changes his life. As the experimental procedure takes effect, Charlie's intelligence expands until it surpasses that of the doctors who engineered his metamorphosis. The experiment seems to be a scientific breakthrough of paramount importance, until Algernon begins his sudden, unexpected deterioration. Will the same happen to Charlie?