Jackie plays Kuo Cheng-Wah, a kindhearted country boy who is quickly cheated out of all his money when he arrives in Hong Kong. Depressed and destitute, he encounters Madame Kao (Ah Lei Gua), a poor woman selling flowers on the street; she urges him to buy a red rose, saying it will bring him luck. He demurs at first, shaking his head sadly, then finally agrees.
His fortunes immediately take a dramatic turn when he stumbles into a gang war, and renders assistance to a dying gang leader. The leader makes Kuo his successor due to a pun, then dies. Kuo, awed, attributes his luck to Madame Kao's rose, and takes to buying one from her every day thereafter.
Kuo starts a nightclub, where he falls in love with a singer (Anita Mui); they vow to do good deeds rather than committing crimes. Before a meeting with a rival boss, Kuo goes to buy his usual rose from Madame Kao, but she is not at her post. He searches for her, and finds her terribly upset over a letter she has just received. The letter is from her daughter, Belle (Gloria Yip), a student in Shanghai whom Madame Kao has been supporting, all the while concealing her sufferings and leading her to believe that she is a rich society woman in Hong Kong. Now, she is coming to visit, bringing her wealthy fiance and his parents, and Madame Kao is afraid that her poverty will bring disgrace on her daughter.
Kuo offers to help, buying Madame Kao expensive new clothes and arranging a lavish party for her, to which he invites some of his disreputable friends on the condition that they impersonate the local dignitaries. Meanwhile, a gang war is in full swing, putting Kuo's life in danger and providing ample opportunity for Jackie Chan's trademark stunts. The climactic stunt sequence consists of a lengthy scene of hand-to-hand combat set in a rope factory.
Miracles is the remake of the 1933 Frank Capra's masterpiece Lady For A Day with Warren William and May Robson.