For the ventriloquist Gabbo his wooden dummy Otto is the only means of expression. When he starts relying more and more on Otto, he starts going mad.

Gabbo, a ventriloquist and a supreme egotist, Mary, his assistant, and Little Otto, Gabbo's dummy, are all performing on a vaudeville circuit; Gabbo constantly finds fault with Mary's efforts to please and insists upon his own greatness. During a performance Mary stumbles and drops a tray, thus infuriating Gabbo, who orders her to her dressing room after the performance, berates her, and finally forces her to leave. Determined to increase his fame, Gabbo becomes featured in The Manhattan Revue, in which Mary is working as a singer and dancer along with her new partner, Frank. More conceited than ever, Gabbo is certain that Mary will return to him. Spying Otto at a cafe, Mary converses with Gabbo through the dummy, and Gabbo realizes that he loves her. Frank sees them together and forbids her to see him again. Learning later of her marriage, Gabbo is driven to madness, and he rushes on stage, disrupting a musical act; during the outburst, he smashes Otto, then realizes him to be his sole object of love and is unable to recognize Mary, who tries to comfort him. He shuffles from the theater with Otto under his arm, shouting hopelessly at the workmen removing the sign advertising "The Great Gabbo."