Stewart stars as the good-natured Elwood P. Dowd, whose constant companion is Harvey, a six-foot tall rabbit that only he can see. To his sister, Veta Louise, Elwood's obsession with Harvey has been a thorn in the side of her plans to marry off her daughter. But when Veta Louise decides to put Elwood in a mental hospital, a hilarious mix-up occurs and she finds herself committed instead. It's then up to Elwood to straighten out the mess with his kindly philosophy, and his "imaginary" friend.