The series was based on the children's book of the same name by the author William Mayne. The show focuses on two friends Keith and David, who stumble upon a weird drumming sound underneath one of the hills that they live near. The hillside opens up one day and the friends find a drummer boy inside of the hill. The drummer boy is from the 18th century and is completely confused on how he came to the 20th century. All three boys must figure out where the drummer boy came from, and how to return him to his home.
David discovers that the candle the drummer boy left behind gives off cold rather than heat and does not burn down. Other strange things are happening - standing stones are moving on the moors, the ground is shaking and all the pigs have disappeared. Obsessed by the candle, David heads underground and does not return. Keith tries to search for his friend, and during the search has a strange encounter with ghostly warriors.