The Circus is generally considered to be a lesser Charlie Chaplin effort, coming as it does between two unquestioned masterpieces, The Gold Rush (1925) and City Lights (1931). To be sure, the film is not one of Chaplin's best, but it has a lot going for it.
Director Chaplin casts star Chaplin in his traditional Little Tramp role, who when first we see him is on the lam from the law. He takes refuge under the tent of a failing circus. Unintentionally, Charlie disrupts the show's big clown act, and the crowd roars. The ringmaster decides to hire Charlie as a clown, building the whole circus around him.
Charlie has many an adventure and close shave while performing under the Big Top, the best of which involves a tightrope, a broken support wire, and a playful monkey. The standard Chaplin pathos rears its head when Charlie falls in love with pretty tightrope walker Merna Kennedy.
When sweet Merna chooses handsome Harry Crocker, Charlie is left alone once more--but, with a characteristic shrug, he shuffles into the horizon and onto his next adventure.
The Circus has several gaping logic holes which tend to pull the film down (we're supposed to believe, for example, that Charlie is unaware that he's a sensation as a clown, even after several weeks of performing before appreciative audiences), but the film contains several excellent setpieces, including a Hall of Mirrors sequence which anticipates Orson Welles' more serious Lady From Shanghai climax by twenty years.
The Circus won Chaplin a special Oscar in 1928, then lay unseen for forty-two years; it was reissued in 1970, with a new musical score by Chaplin himself (who can be heard singing the theme song in the opening scenes).