On the rainy afternoon of Sarah's fourteenth birthday, her parents and her favorite Aunt Jenny take her for a picnic in a greenhouse. There Sarah discovers a mysterious door which, once she touches it, opens to reveal another world, one that leads her on a quest to save Hutanya, a devastated land which was once covered with lush rainforests but is now virtually devoid of life.
Upon entering this land, Sarah meets Will, a child of the Old Magic, who tells her that he believes she is Sareka, a sorceress who disappeared from Hutanya twelve years before and that her return has been awaited. Will is accompanied by a lizard, Ashrok, for whom Sarah develops an immediate aversion. Will leads her to the caves of Karst, which are covered with huge murals of the lost forest life. Here Sarah meets Marwa, an ancient wizard who also believes that she is the lost Sareka. Sarah learns that Sareka disappeared when Marwa sent her to stop Asher, a sorcerer who had gone over to the dark, from draining the waters which led to the destruction of the rainforest. Asher commands an army of wraiths, who drink and then later spew the water on the mountains in the far north where it freezes. Asher has also locked the Great Falls, the source of all water in Hutanya, in his icy spell. Because the water is disappearing, Hutanya's people, plants and wild life have almost all died out. Only the Godawa, a nomadic tribe to the south, and the Dasai of the High Plains, led by the famous Rein, still remain.
Marwa tells Sarah that only Sareka can defeat Asher, and that she must travel to the north to confront him. The wizard is reluctant to tell her about Sareka's past, as he believes that her memories must come on their own accord. At first, Sarah doesn't believe she has anything to do with this world or any power to help, but gradually, with Marwa's guidance, she begins to awaken to Sareka's memories. When the day comes that the old wizard realizes the wraiths may have found the caves, he sends Sarah and Will that very night on their journey to the north, accompanied only by the batlings, Archana and Calum, who serve as their scouts, and the ever-present Ashrok.
So begins Sarah's quest to free the waters of Hutanya.