The Secret Seven have a new meeting place - a treehouse! But someone else is using it too. The gang are furious, but then they learn the intruder is in big trouble and needs their help. Can the Seven come to the rescue..? The secret seven are delighted with their new treehouse in Windy Wood. That is , until they discover that a stranger has been living there in secret! But the gang's shock soon turns to concern when they learn their uninvited guest is caught up in a dangerous mystery. Can the friends get to the bottom of things before it's too late?