Tom, Janet, Emily, James, and Peter become friends and form their secret group called, 'The Adventurers'. The children attend the local Greythorpe High School in Crawbridge. Tom lives with his Uncle Herbert and he arranges secret meetings for the group in his uncle's garage. Together with Baxter the sheepdog, as the Adventurers, they are ready to solve a mystery! It is Christmas time and soon, they are on the trail to locate Lady Fairdale's missing diamond necklace! What clues will the Adventurers find in the St John's Church graveyard? Where does the secret passage lead to? What adventures lie in store and who is the mysterious new schoolmaster at Greythorpe High? Why not join the children as they seek to find Lady Fairdale's diamond necklace. If you would like to find out more about this mystery, it's time to meet the Adventurers!