This is the story of a girl from an orphanage. After a bit where she spins a fellow orphan a tale about how she was lost, a woman comes to the orphanage for a second housemaid at the house of Mr. Fountain, alchemist, and member of the royal court.
She meets there the cook, Bill who's friendly, Susan, the first housemaid, who's not -- Freddie, Mr. Fountain's apprentice, Isabelle his daughter -- and discovers the house is very odd to her, though not to her fellow servants. Plus Gus, the cat, will talk to her as he won't/can't talk to the others. Freddie discovers her abilities, and despite being snobbish and never having had to do anything in his life, turns out not half bad. But Rose just wants to be the housemaid and earn her living.
Meanwhile, children are vanishing, and the widowed Mr. Fountain is interested in the lovely Miss Sparrow.
Action and adventure ensue. Involving breaking a mirror, climbing down plants on walls, a stuffed bear, a cheap locket, using a marble for light, and much more.