Fire spell, or, Splendours and glooms - Laura Amy Schlitz

Clara disappears on her birthday. Exceptionally wealthy and exceptionally lonely, she requested that a puppeteer and his two orphan helpers stage a spellbinding show for her in the vast empty house. But then the curtains close and darkness falls ...The puppeteer, Grisini, kidnaps Clara and uses his sinister powers to imprison her body and mind in the form of a marionette. His two young assistants realise what has happened, and all three children find themselves caught up in a terrible struggle for supernatural eminence between Grisini and a dying witch of extraordinary power.The bewitching and brilliant magical adventure Fire Spell, published in the USA as Splendors and Glooms , was awarded the Newbery Medal Honor and is a New York Times bestseller.