Jane had gone to the seaside to stay at Bella Vista Holiday home while her parents were away. On the beach Jane found an old metal box. Unable to open it she hid in the ruins of Roule Castle, returning later with her friend, Ben. When they uncovered the box they were chases by some sinister men who were also after the box, they managed to escape.
One night all the children in the town where Louisa lived, were summoned by a mysterious light that settled on top of a nearby hill. The children were never seen again except for Louisa who had been too slow ro join them because of her lame leg. However the urge to find the mysterious light caused Louisa to leave home with her her dog, Toby.
Amy and Ruth had been invited to spend a fortnight with their great aunt Maude although they had never met her. After arriving they were told by her employees, the Clydes, that she was ill and couldn’t be seen.
The Freemantle family had a mystery guest, a girl called Cathy, who had lost her memory after a fall from a horse. When two men from the mysterious Alpha Project broke into their house search for Cathy she decided to move someplace else. Lindsay Freemantle went with her to help her.
During the war Rita Cooper and her brother Rolly were among the school children evacuated from London. They were sent to Great Tor a forbidding old mansion in Cornwall. While staying there the youngsters discovered that the domestic staff had a hoard of stolen treasure hidden in a cave under the house.
Brenda and her young sister, Dulcie, were evacuated from London and sent to live with Mrs Outing in a small village in the country during the war. Brenda and, Dulcie made friends with a local boy named Jem and together the three spied on Mrs Outing who acted very strangely and mysteriously at nights. Brenda overheard, Mrs Outing in her room speaking in a foreign language which she thought to be German.
When Mr Ridgeway dies he leaves his house and possessions to Alison Kirk, whose uncle and aunt are servants there. Years before, Alison had discovered a beautifully kept secret garden on the property. The blue windmill is carved on the entrance to the garden. When Alison revisits the garden she is shocked to find someone has trashed it. Alison’s Uncle James thinks it has something to do with Groot, a Dutchman who was present at the reading of Mr Ridgeway’s will, because it was at that point Mr Ridgeway forbade Uncle James to go into the garden. Mr Ridgeway also left a secret message for Alison, and Groot makes a grab for it. He fails, and the message is a key to a safe deposit box. When Alison opens the safe deposit box, she is astonished to find it contains a chrysanthemum.
Susan Smart is managing her father’s winter sports school in Switzerland after a deliberate attempt on his life put him in hospital. The same enemy is now trying to drive Susan out of the chalet and putting her life in danger. A threatening motive indicates the enemy’s motive is to buy them out.
When their car disappeared on a touring holiday, sisters, Ann and Beth, found themselves prisoners in a strange village. It was run by a man named Volin and there were two types of people: Alphas who were in charge and Betas who obeyed them.
Young Caroline was mute since her parents were killed by a highwayman. Then she was taken from the workhouse to work for Miss Abigail in her large gloomy mansion. Caroline discovered the house was also being used as a hideout for highwaymen and also that a girl was being held prisoner somewhere in the building. Some cats which roamed the house were Caroline’s only friends.