About the book: year / What a pity that Peter's mother decided to renovate the barn in which the Secret Seven always gathered during the holidays ! The guys have to look for a new shelter and they choose an old fenced cave for their meetings. But on the very first night, someone breaks in and steals their things. Who could it be? Is it really Susie, Jack's bad sister? But how could she get into the cave without touching the threads pulled by the guys? The Secret Seven begin a new investigation…