This tear was a different sort. As it fell from scales to the air it hardened and gleamed clear as ice, and formed into a diamond. Humbert hummed again but not a sad hum. This was the hum of a dragon that had just received a promise as unbreakable as diamond.

Avis has a dream to work with animals, so when a scientist with a witchy-looking house offers her a job as a pet-sitter she jumps at the chance. But it turns out Avis is not looking after pets at all – the animals in Dr Malinda Childes' backyard are as eccentric as she is and Avis has to promise to keep them a secret.

But one promise and one secret leads to more promises and more secrets and before long Avis finds herself overwhelmed by promises and secrets and responsibilities and one very BIG chocolatey dragonish problem.