Reporter Yu Mong-yuen is recovering from a leg injury in his fiancee Man-wah's apartment. Bored, he looks out the rear window and observes the life of the neighbouring building. Among the tenants are a sugar-daddy and his mistress, a middle-aged man wants to marry a young girl, but she is in love with his son. Finally, she hatches a plot and makes the man agree to her marrying his son ; a sly fortune-teller ; a lively gym, a rich widow quarrels with the trainer of a gymnasium because his dog has bitten her cat ; and an opera school, a woman signs, leaning on the balcony, and a man tries to strangle her. In fact they are rehearsing an opera…… One evening, Wah is on the night shift, and Yuen watches the opera troupe rehearse to the end. Under the influence of drugs, Yu mistakenly believes that a divorced man has murdered a taxi dancer. He alerts the police, but the whole thing is nothing more than a misunderstanding.