When Milly invites her best friend Cora to the family cabin way up in the Northwoods, she thought the week would be filled with swimming, canoeing, and exploring. Instead, her beloved dog Angus runs away, and the girls must fight the clock to find him so he can take his vital medicine. If that wasn't bad enough, Milly and Cora learn that a wealthy developer plans to clearcut the lake's pristine forest, putting all the family cabins around the lake in jeopardy, not to mention the wildlife. Join the adventurous girls as they try to save the lake and find Angus!