Once there was a gypsy queen who wore on her wrist a chain of six lucky charms. The queen gave each her six children one of the charms as their lucky talisman, but ever since the chain was broken, the gypsies have been dogged with misfortune.
Luka and Emilia must travel to the New Forest to find the Wood tribe, whose charm is a rue flower, the herb of grace. Its power is that of plants and herbs - which can both heal and poison.
On the way, the two children tangle with an impoverished widow, the thief-taker Coldham, a highwayman, and a witch, and find themselves caught up in a Royalist plot to restore King Charles II to his throne.