Dragons are common in the backwater kingdom of Bellemontagne, coming in sizes from mouselike vermin all the way up to the fabled Kings, which haven't been seen in an age. Gaius Aurelius Constantine Heliogabalus Thrax (who would much rather people call him Robert) has recently inherited his deceased father's job as a dragon exterminator, a career he detests with all his heart. Things turn from bad to worse when Robert is hired by the royal family to disinfest the entire castle, as Princess Cerise is determined to receive Crown Prince Reginald with the shabby château looking its best.

What happens next is not the fairy tale you may be expecting.