The Bad Beginning is the first book in A Series of Unfortunate Events, children's novels which follow the adventures of the three Baudelaire orphans Violet, Klaus, and Sunny. After their parents are killed in a fire, the children are sent to live with their deceitful cousin Count Olaf, who aims to steal their fortune. Though the narrative maintains a comic tone, the children endure many Olaf's evil schemes, including an attempt to marry fourteen-year-old Violet, before they are able to escape.
Violet Baudelaire is aged fourteen and has a love for inventions; Klaus Baudelaire is twelve and an avid reader; Sunny Baudelaire is a baby who uses words only her siblings and parents understand, and enjoys biting. The children are told that their parents died in a fire which also destroyed their house. Mr. Poe, who gives them this news, is a banker whose job it becomes to find a guardian for the Baudelaires. He is also in charge of the large Baudelaire fortune, which Violet will inherit when she turns eighteen. He places them into the care of Count Olaf. Olaf's house is filthy and covered in disconcerting eye images; it has a tower which the Baudelaires are forbidden from entering. Count Olaf is unpleasant, easily angered and forces the children to perform many laborious chores.
One day, the Baudelaires are set the task of making dinner for Olaf and his theatre troupe. They make puttanesca, but when Olaf arrives he demands roast beef. The children reminded him that he never asked them to make roast beef and Olaf becomes angry, striking Klaus across the face because he gets angry that the children announce to everyone that he has only given them one bed.
Olaf gives the children roles in his new play, in which Violet will marry Olaf. The children realize something is amiss and use Justice Strauss' library to research law. Klaus learns that the marriage in the play will be legally binding and that Olaf can inherit their fortune from it. He confronts Olaf, who gets one of his associates to put Sunny in a bird cage, dangling from outside the window of his tower. He threatens to kill her if Klaus and Violet do not follow his plan. Violet constructs a makeshift grappling hook and uses it to climb up the tower. She finds the hook-handed man (a member of Olaf's theatre troupe) waiting to capture her. Klaus is brought up to the tower and they are locked together in the room until the play begins.
After Violet signs the marriage document, Olaf interrupts to tell the audience that their wedding was legally binding. Justice Strauss and Mr. Poe both object, but concede that the law requires them to hand over the Baudelaire fortune to Olaf. Violet interrupts to proclaim that the marriage was not legally binding, as she signed with her left hand despite being right-handed. Justice Strauss agrees that this invalidates the marriage. Before Olaf can be arrested for locking up Sunny, one of his associates turns the lights in the theatre off and he is able to escape. Justice Strauss tells the Baudelaires that she is willing to adopt them; however, Mr. Poe says that this would go against their parents' will and takes them back to his household until he can find another guardian for them.