Redmond O'Hanlon is a British author, born in 1947. Mr. O'Hanlon has become known for his journeys into some of the most remote jungles of the world, in Borneo, the Amazon basin and Congo. He has also written a harrowing account of a trip to the North Atlantic on a trawler.
Rachel is a quiet, imaginative twelve year old girl who likes to write stories and prefers to be lost in a world of her own. One day, she is given a mysterious door as a present by Mr. Pelf, a strange man who sells secondhand treasures like shards of stained glass, dolls' eyes, and ribbons from the back of his truck. Everyone in Rachel's neighborhood thinks warmly of Mr. Pelf, but she has always disliked him. She is frightened of the door and refuses to enter it, though her little brother and other children on the street enjoy playing with the door. Mr. Pelf tells her that soon everyone will forget the door, only she will know it is there. It is not until Rachel finds a glass prism while exploring outside that she decides to walk through the curious door.
Inside, she discovers a pale world mirroring her own. She meets lost children here who call themselves Gatherers. They are hollow and eyeless, and wish for Rachel to stay with them. She learns that Mr. Pelf is the Master Gatherer, and holds the children captive so that they can search for lost items. When Rachel looks through the glass prism, she is able to see a path back to the door, and runs for it as the children chase her. Once she has escaped back into her world, the door becomes invisible and Rachel falls ill. Everyone around her forgets the door ever existed, and she slowly recovers. But her next-door neighbor, Ralph, disappears, and Rachel knows that he has gone through the invisible door. It is up to her to save him from becoming like the other hollow children.