London, 1920s. Sid Nichols is one half of the comedy duo, The Trojan Brothers, one of the city's most celebrated shows. His role is as the back-end of a pantomime horse with his dear friend, Benny, leading from the front. Every night they take the music halls by storm, picking members of the audience to ridicule to the amusement of all present.

Yet one night Sid meets his match when he spots his long-lost cousin, Betty Todd, sitting in the aisles. A battle of wits ensues and Sid becomes enamoured with his new sparring partner, much to the dismay of Benny and his wife. For them it is obvious that a woman of Betty's social class will not take a man like Sid seriously. He will only be hurt and humiliated.

However Sid is determined to pursue this dangerous affair, and as his infatuation for Betty grows, he is driven to the edge of insanity by this woman's games. It soon becomes clear that what started out as a simple amusement will lead to the most devastating conclusion.