Frank and Joe help their father with saving the valuable Bay Diamond from being stolen at the Bayport Museum. However, the gang turns the tables and steals the diamond. The Hardys, with Chet’s assistance, uncover an even more sinister plot that must be stopped!

As summer vacation begins, Chet Morton’s father opens up an arcade on the Bayport waterfront. Things quickly sour on opening day when the arcade is threatened by protestors, as well as a business rival. The threats against the arcade become more aggressive as Frank and Joe help Mr. Morton by providing security while also investigating who’s behind the threats and sabotage attempts

Frank and Joe are tasked to help Fenton Hardy and Sam Radley with busting a crab smuggling operation in the Alaskan waters. Fenton is kidnapped in Seattle, and the boys, with Sam’s help, go undercover as crab fishermen to solve this case.