The Watson children, Nicholas, David, Helen and Roland, wander towards a street which Roland randomly selected from a map of
Manchester. This fictional street is later revealed to be roughly in the
Newton Heath area, which is undergoing
slum clearance. The neighbourhood is deserted except for a strange fiddler. Roland kicks a ball into the window of a partly demolished church. When his three siblings, who separately entered the church to retrieve the ball, all fail to return, Roland follows. The fiddler's music opens a portal to the world of Elidor and he instructs Roland to step through. The music leads Roland through a barren castle and a desolate forest, to the Mound of Vandwy (a reference to the artificial
Silbury Hill), where Roland mentally battles a
stone circle that seems alive. The fiddler, Malebron, then reveals himself and says the other siblings are in the mound. To enter, Roland must picture the porch of the family's new home in his mind, which causes it to appear on the hillside. Inside, Helen, David and Nicholas are entranced by a tree, whose spell Roland breaks by severing it with a spear Malebron gave him. The other children find a cauldron, sword and keystone before exiting. With the spear, these are the Four Treasures of Elidor. Malebron explains the children are part of a prophesy. Elidor is being overcome by an unspecified darkness and can only be saved by hearing the Song of Findhorn. Should Elidor perish, it "would not be without echo in [the children's] world". The darkness chases the children back to where Malebron opened the portal. He says they must keep the Treasures safe in England. The children emerge back in the church where no time has passed and the Treasures have become mundane objects, but they are later found to interfere with electronics and give off static electricity. The children bury the Treasures in a
Faraday cage in their garden. While digging, Helen finds a vase with a unicorn picture and a cryptic inscription, later revealed to mean that only a woman can communicate with the unicorn. Over the next year, Nicholas rationalises their experience as a "mass hallucination", but Roland, having imagined their front door to enter Vandwy, believes that strange rattling sounds mean it is still connected to Elidor. He also sees shadows above the Treasures which have no real counterpart. At a Christmas party, Roland is made to operate a
planchette in a
séance. He writes "Malebron", draws a unicorn and writes "Findhorn". On the way home, a unicorn suddenly appears in the mist. David thinks the static comes from Elidor in an attempt to home in on the signal from the buried Treasures. When all four children observe the shadows, they resolve into Elidor men who escape into the Manchester suburbs. After the Watson parents go out for a party, the children dig up the Treasures but are not sure what to do with them. The door rattling intensifies and they decide they cannot remain in the house while it is dark. They encounter a drunk bus passenger who reports seeing a unicorn, and the bus happens to take them back to the church from which they entered Elidor. In the dark, the children are separated. Roland finds Findhorn fighting the Elidor men. David and Nicholas turn up but Findhorn ignores their pleas for him to sing. Helen finds Findhorn and appears to listen to her. The men kill Findhorn whereupon he sings; a portal to Elidor opens showing the darkness gone. The children toss the Treasures into the portal where they resume their original form, and the story abruptly ends with the children alone in the slum. ==Title==