There is no warning. No chance to prepare. They arrive in the night: thundering up through the ground, transforming streets and towns into shadowy forest. Buildings are destroyed. Broken bodies, still wrapped in tattered bed linen, hang among the twitching leaves. Adrien Thomas has never been much of a hero. But when he realises that no help is coming, he ventures out into this unrecognisable world. Michelle, his wife, is across the sea in Ireland and he has no way of knowing whether the trees have come for her too. Then Adrien meets green-fingered Hannah and her teenage son Seb. Together, they set out to find Hannah's forester brother, to reunite Adrien with his wife and to discover just how deep the forest goes. Their journey will take them to a place of terrible beauty and violence, to the dark heart of nature and the darkness inside themselves.