While out tagging one night, Meg witnesses the dying moments of a fox... a fox that shapeshifts into a man. As he dies, he gives Meg a beautiful and mysterious gemstone. It isn't long before Meg realises that she's also inherited his power to shift and finds an incredible new freedom in fox form.
She is plunged into the shadowy underworld of London, the territory of the five warring groups of shapeshifters - the Skulk, the Rabble, the Conspiracy, the Horde, and the Cluster. Someone is after her gemstone, however, someone who can twist nature to his will. Meg must discover the secret of the stone and unite the shapeshifters before her dream of freedom turns into a nightmare.