Elidor — Alan Garner

A mechanical street map, a deserted slum, a church in ruins, and a football--four ordinary things that lead the Watson children into an extraordinary adventure in the land called Elidor, a magical world one step removed from our own. In pursuit of four ancient Treasures, the forces of evil have crossed over into our world. It falls to the Watson children to find the Treasures, seal the bridge between worlds, and guard the strayed unicorn Findhorn . . . even though their heroism may cost them everything.