When Elwood P. Dowd starts to introduce his imaginary friend, Harvey, a six-and-a-half-foot rabbit, to guests at a society party, his sister, Veta, has seen as much of his eccentric behavior as she can tolerate. She decides to have him committed to a sanitarium to spare her daughter, Myrtle Mae, and their family from future embarrassment. Problems arise. Only at the end does Veta realize that maybe Harvey isn't so bad after all.