Eleven-year-old Nicholas Vargas thinks his sucky life has been turned upside down. His developer father has remarried and moved his new wife and daughter into his home in the soon-to-be-completed Melgrove Hollow. So, not only has Nick lost his bedroom to his wacko new step-sister, Laurie (who lugs around this huge book about faeries and wishes her name was Lauranathana...C'mon! How lame is that?!), but his father actually wants him to spend time with her.
When an "expedition" to a nearby lake turns up a nixie with a giant problem - and by giant we're talkin' the huge, lumbering, fire-breathing variety - it's up to Nick and Laurie (with the help of Nick's big brother, Julian) to figure out the best way to stop the rampaging beast before all of Mangrove Hollow goes up in smoke!