While on summer vacation, Bloom, an ordinary 16-year-old high school girl living on Earth, encounters a battle between a 17-year-old fairy named Stella and an ogre named Knut. As Stella's magic scepter is stolen, Bloom intervenes, discovering that she has magical powers and manages to turn the tide. Stella invites Bloom to attend Alfea, a school for fairies, to fully master her new powers. Knut returns with more ghouls and a troll, launching a surprise attack at Bloom's home. Stella and Bloom call in the Specialists, a group of boys from Magix, who capture the troll and defeat Knut. The next morning, Bloom has agreed to go to Alfea.
Bloom arrives at Alfea, under the name Princess Varanda of Callisto, a student who had declined her admission. She is introduced to her apartment mates, Musa, Tecna, and Flora. The girls then go for a day out in Magix City. While calling her parents, she spots Knut spying on her friends, and follows him. She learns that Knut is working for the Trix: three witches from the school of Cloud Tower named Icy, Darcy, and Stormy. After pitifully trying to defend herself, Bloom is captured by the Trix, but the other girls rescue her. Bloom reveals her real name. When the girls are caught sneaking back into school, Bloom confesses her real name to Headmistress Faragonda and discipline head Griselda, but Faragonda forgives her transgression and lets her attend the school. The girls agree on Bloom's name for their group: The Winx.