An English girl, a Polish refugee, and a displaced boy from the Orient explore an island-strewn river flowing past the ancient manor house of Green Knowe.
The inhabitants of Green Knowe become involved with black magic when a modern-day witch attempts to find books of witchcraft supposedly hidden in the old house by a mad seventeenth-century alchemist.
A strange friendship develops between a young Chinese refugee who is spending the summer at Green Knowe and a gorilla who has escaped from the London Zoo.
While eagerly following each stage of the new stone manor house his father is building to replace their old wooden Saxon hall, a young boy, part Saxon and part Norman, becomes involved with ancient magic that carries him through time.
