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.

A hitman, Leroy Davis, McGarrett's father failed to arrest comes to McGarrett to finally confess his crimes and admit where he buried his victims. Also, Jessie makes a dangerous decision that could ruin Adam's life.