McGarrett and Danny investigate the murder of a private detective whose client was killed the same way, and Adam sends Jessie into a dangerous situation with disastrous consequences. Also, Danny's uncle, Vito, comes to town to help Danny and McGarrett get their restaurant up and running.

Adam's mission to take down organized crime on the Island goes sideways when deadly chlorine gas he was using to bait a big fish falls into the wrong hands. Also, Adam begins to doubt Jessie's allegiance.