When twelve year old Joe Mitchell, along with his two younger sisters, arrive at the sleepy seaside town of Smugglers Cove, they're expecting a quiet and uneventful holiday. But before long they fall into one adventure after another. Following their escapades in The Mystery of Adventure Island, the children are anticipating a quiet time at Willow Lake. However, strange things happen and it doesn't take long before they realize that something mysterious is going on.