The Secret of the Old Towers

The famous five set off to the snowy Welsh mountains. The kids can't wait to go sledding and skiing. They are having a great time, but one day they notice an old woman in the window of a mysterious house, who is giving them some signs. The friends suspect that she is being held captive in the «Old Towers» and decide to find out if this is true. What if the imprisonment of the prisoner is somehow related to the extraction of rare ore in the mountains?