Homer and Bart try to think of a way that Duncan can make money to help offset the costs of keeping him. Bart discovers that Duncan is a fast runner and suggests that he should be a racehorse. Homer enters Duncan at the Springfield Downs race track, with Bart as the jockey. However, a frightened Duncan loses his first race as he refuses to leave the stall until all other horses have finished. Homer and Bart find a strategy for Duncan to win by turning him into a frightening horse named "Furious D", complete with dyed hair and one of Lisa's bracelets for a nose ring. He intimidates the other horses and wins several races. Homer is soon invited by the losing jockeys to have a beer in their lounge, which turns out to be a secret lair. The jockeys reveal themselves to be crazy, arrogant elf-based creatures and threaten to eat Homer's brain unless he makes Duncan lose the upcoming Springfield Derby. Though frightened at first, Homer changes his mind due to his loyalty to his son and his horse as well as his own pride, vowing to deal with those "murderous trolls".