Complex sentence: In "Harry Potter and the Prisoner of Azkaban", during Harry's third year, Cedric captained the Hufflepuff Quidditch team which beat Gryffindor when Harry Potter fell off his broom owing to the presence of Dementors.
Split into simpler sentences: In "Harry Potter and the Prisoner of Azkaban", during Harry's third year, Cedric captained the Hufflepuff Quidditch team. However, he beat Gryffindor when Harry Potter fell off his broom owing to the presence of Dementors.