Williams plays Dr. Malcolm Sayer, a shy research physician who uses an experimental drug to "awaken" the catatonic victims of a rare disease. DeNiro co-stars as Leonard, the first patient to receive the controversial treatment. His awakening, filled with awe and enthusiasm, proves a rebirth for Sayer, too, as the exuberant patient reveals life's simple - but unutterably sweet - pleasures to the introverted doctor. Encouraged by Leonard's stunning recovery, Sayer administers the drug to other patients. The story of their friendship during this emotional journey is a testament to both the tenderness of the human heart and the strength of the human soul.