George Barnard's life is turned upside down when she and her cousins embark on a treasure hunt. Soon, they find themselves battling a merciless enemy who wants to change the world.

The Five are reunited by mysterious letters sent by an old friend at the spooky Prospect Hotel. Their mission? To solve a murder. The twist? It hasn’t happened yet.

When Uncle Quentin's life's work is stolen from Kirrin Cottage, the Famous Five take the night train to Scotland and are drawn into a deadly game of espionage, theft and deceit.

As the summer comes to an end, George sets in motion a final adventure to protect a circus magician from an unscrupulous doctor who wishes to make use of his powers in the clinic.