Twelve-year-old Alistair Cleary lives in a town where everyone knows each other. One afternoon, his neighbor, Fiona, shows up at Alistair's doorstep with a strange proposition. She wants him to write her biography because in her basement there's a gateway that leads to the magical world of Aquavania, the place where stories are born. In Aquavania, there's a creature called the Riverman and he's stealing the souls of children. And Fiona's soul could be next.