A Sorcerer in the seventeenth century plans to control time, and thus the World. Emma, Tom, and their parents live a 'normal life' in the present day, until a letter arrives one morning requesting the father's attendance at a meeting in another part of the Country, later that same day.
Whilst travelling to the meeting, Emma and Tom's father is involved in a road accident. This leaves him unconscious, and fighting for his life miles away from the family home. The mother needs to be with her husband; the children need to be cared for. The solution is to send Emma and Tom away to the West Country, to stay with their Great Aunt Hilda at Tanglewood. Emma has not seen her Great Aunt for some considerable time. Tom has never met her. Neither child wants to go.
Whilst at Tanglewood, the children meet various beings and creatures, including elves, a dwarf, and a dog that can talk. The elves explain that the sorcerer tricked the dwarf into stealing the Moonstone, which gives life to the Elven World. The elves cannot leave their World, and must, therefore, seek the assistance of others to recover the Moonstone, and thus save their world.