the portal in the attic

When Cassandra and her young brother are lured into a portal in their attic to another world by a strange man called Wangi, little did they know why. Cassandra is surprised and delighted to be in a world of beauty and friendliness--the land of Sumer. It soon becomes apparent however that the only reason she is here is to cross a mysterious river, and seek out a prince and give him a certain item. Only then can she return to Earth again. Unknown to her the land beyond the mysterious river is ruled over by a suppressive regime called The Rann. There she is interrogated. She flees with the prince after a murder and they seek shelter in a forest. There he tells her the history of his world, and his plans to destroy The Rann.