The award-winning reader series is specially designed for young adults and includes original stories, adapted fiction, and fact books. The series continues the adventures of twins Andy and Mary, known from "A Little Trouble in Amsterdam" at Level 2. This time, Andy and Mary are with their father in the beautiful Yorkshire Dales in the United Kingdom. When they discover a locked door in a seemingly abandoned mine, Mary's curiosity is piqued. What is hidden in the mine? And who is the man watching them with binoculars? This book is published in British English. The full audio recording of this book and additional teaching materials are available for download at cambridge.org/experience-readers. Cambridge Experience Readers inspire teenagers to get hooked on reading.