The High Crusade by Poul Anderson is a vintage science fiction novel published in 1960. The story is set in medieval England and follows the adventures of a group of knights who are abducted by aliens from a distant planet. The knights, led by Sir Roger, manage to take control of the alien spaceship and decide to use it to conquer the alien planet. Along the way, they encounter various challenges and obstacles, including a hostile alien race and a traitor in their midst. The novel is a humorous and satirical take on the traditional medieval knight tale, with elements of science fiction and adventure.