At a carnival boxing tournament in England, handsome Johnny Flanagan, an amateur boxer, jumps into the ring from the audience to challenge one of the professionals. After Johnny easily wins the fight, he and his trainer, Charlie Sullivan, collect his winnings from Charlie’s old friend, boxing manager Sharkey. Sharkey agrees to help get Johnny professional representation and introduces them to Giuseppe Vecchi, a prominent promoter in London. Italian Giuseppe receives the three men warmly although his beautiful American wife, Lorna, immediately dislikes Johnny and is insulting to him. Later, Johnny vows to Sharkey that he will “show that dame.” When Johnny wins that night’s carnival boxing match, Giuseppe agrees to a partnership, inviting the entire group to train at his estate in Stratford-on-Avon. There Johnny, Sharkey and Charlie work out in a barn and jog around the small lake while Giuseppe fishes and relaxes. Giuseppe encourages a family atmosphere and is puzzled by the animosity between Lorna and Johnny, failing to notice the sexual tension between them. Hoping to ease the situation, Giuseppe throws a birthday celebration for Lorna at a nightclub and insists that she and Johnny dance together. Lorna draws Johnny close to her as they dance and they declare a truce. Later that night after Giuseppe has fallen asleep drunk, Sharkey sees Lorna and Johnny kissing. Johnny’s training suffers as a result of the ensuing romance between him and Lorna. After a guilty conscience soon prompts Johnny to break up with Lorna, she attempts to throw herself into the path of an oncoming train rather than spend the rest of her life with a man she loathes. Johnny rescues her and the next morning Sharkey advises Lorna to stay away from Johnny. The entourage, minus Lorna, heads to London to prepare for their first big match. Just before the fight, Johnny receives a brief phone call from Lorna telling him she is pregnant. The bout begins well but when Johnny sees Lorna sitting ringside with Giuseppe, the distraction causes him to lose the fight. Giuseppe is sorely disappointed, but still unaware of the affair, good-naturedly offers to continue housing the group at his estate until they can make other arrangements. Before they leave London, Lorna urges Johnny to kill Giuseppe, but he is horrified by the suggestion. Although Johnny offers to marry and support her, the greedy former taxi-dancer rejects his earnest intent. After Lorna overhears Sharkey’s plans to take Charlie and Johnny to a carnival in Scotland, she announces her pregnancy to Giuseppe. Giuseppe is thrilled by the prospect of fatherhood and celebrates by getting drunk. Johnny privately confronts Lorna, who successfully convinces him to kill Giuseppe, and proffers some poison she obtained in London. The next day, Johnny pretends to go for a bicycle ride; instead he swims into the lake and drowns Giuseppe while he is fishing. Giuseppe’s Italian mother and sister arrive for the funeral and indicate they are suspicious of Lorna, but the police inquest determines the death was accidental. Before Giuseppe’s family leaves, the mother announces that she has seen through Lorna’s fake pregnancy. Overwhelmed by remorse, Johnny refuses to leave his room, and dies after Lorna secretly poisons a bowl of soup that Sharkey brings him. Sharkey finds the remaining poison and assumes that Lorna drove him to suicide, so he and Charlie plant the poison tablets in her bedroom and call the police. Lorna is arrested for murder and Sharkey and Charlie return to setting up boxing matches at carnivals.