The Hardy Boys. The best crime fighting team ever! Each one couldn't solve the mystery without each other. They are a team, and Frank Hardy and Joe Hardy are often in one sentence and never separated. They are the best siblings to each other ever. But an argument threatens to split their strong brotherly bond and each decide to try and solve mysteries without each other. Soon they are hired by the same man, Mr. Barstow, who needs them to find his son, who was presumably kidnapped by the Assassins, a cruel ruthless group who will do anything for riches. A note comes and threatens Mr. Barstow, saying that if he did not give the Assassins what they want't his son would be killed. The mystery starts to tear Frank and Joe apart and the mystery is falling apart also. Can they pull back together in time to solve the mystery before it is to late?

When Frank and Joe Hardy and their friend Tony Prito crash land in a lake in Idaho, they're just glad to be alive. However, they soon learn that the people who live on the town next to the lake are stranded by a washed-out bridge and that one of the townspeople has disappeared. To make matters worse, nearly everyone is blaming their troubles on a lake monster. Frank and Joe are skeptical about that, and they set out to solve the mystery, which turns out to be much bigger than they realize.