From book cover:

Holly could hear the blood pounding in her ears. She looked cautiously round the corner into the hall. It was deserted. 'Come on,' she whispered. 'It's our only chance.'

Suddenly there came an ominous sound: a key turning in a lock. Holly ran for the doors, but she was too late. The caretaker had locked them in with the two dangerous men...

There’s nothing 15-year-old Holly Adams loves more than a good mystery. So she sets up The Mystery Club to meet people who share her interest. But only two people want to join - energetic Tracy Foster and carefree Belinda Hayes. The three girls couldn’t be more different, but they quickly become best friends. And when they stumble on the clues to a lost fortune, suddenly The Mystery Club is involved in an adventure that’s only too real. Before they know it, they’re on a roller-coaster of mystery, danger and suspense!