The Adventures of Marco and Carla: The Monster of Lake Shan is the 3rd installment in this Tween series. Geared towards 13 and under this series is filled with mystery, adventure, and all kinds of creatures. In The Monster of Lake Shan, our main characters, Marco, Carla, and their friend Sammie go on a short vacation with their families. On the way their Marco becomes interested in the tale that there is some kind of creature that lives in Lake Shan and it wasn't something nice. When they get to the lake, everyone is having a good time, until someone disappears. The race is on to find out about the monster and how to get rid of it before it takes someone else.