The Lighthouse at the World's End

Adventurous, magical and brilliantly funny final book in the House at the Edge of Magic series.
Nine and her friends are headed to the mortal realm in search of the only thing that will shake a very tricky witch off their tail: a priceless stargold locket. It lies hidden in the Nest of a Thousand Treasures, guarded by Nine’s old foe – the formidable gangmaster of all the thieflings in London.