The sun-bleached, lopsided wooden town sign decorates the side of the new highway through the desert. Someone has thoughtfully painted the population statistics on it: 5000 3502 2006 1545 810 200. Grymm, the dripping, blood-red paint reveals, is a place you leave.

Instead, thanks to a job offer that George Lipton and his wife cannot afford to ignore, squabbling step-siblings Jacob Daniels, 11, and Wilhelmina Lipton, 13, are rushing towards it. And worst of all they have to put up with their hated, caterwauling six-month-old half-brother, Bryan.

Grymm perches on the edge of the desert and from the moment Jacob and Mina enter the town they sense something is wrong. From Thespa Grymm, the grotesque letting agent who seems to want to eat their baby brother, to a cafe owner whose milkshakes might contain actual maggots and the creepy, hairless butcher, Cleaver Flay, all is not what it seems.

Then, overnight, baby Bryan disappears, as if he never even existed. And that's when things get seriously weird.

Together, the children have to find out what happened to Bryan, a quest which takes them to Thespa, who knows all the town's secrets - from the massacre of the land's original inhabitants to the murder of the Chinese miners who first discovered gold there.

Along the way they encounter Malahide Fleur, the town baker, Beersheba Bluehammer, frustrated artists and hardware store owner, as well as the vampiric Puzzlewicks, an identical husband-and-wife team who make darkly fantastical candles in their factory on the edge of town.

All roads eventually lead to the creepy and insect-like Mr Anhanga, the mine owner, and the fake gold rings that the inhabitants all wear. Suddenly the children realise that it's not just the missing Bryan and themselves that are in danger - Anhanga has plans to turn the whole world Grymm.