The episode opened with a pirate radio station DJ named Bobby Raines being blown up when he hit a sound effects button. As Steve and Danny began to look into the murder of Raines the trail led them to a retired NY Cop named Tony Archer.
It turned out that Tony was a good friend of the Raines and wanted to help Danny and Steve catch the killer. He also had some valuable insight on the people that Raines had been coming in contact with. After Max determined the bomb was made from illegal fireworks, Tony remembered that a man name Doug Leland matched the description of the guy who bought them.
Not being able to find Leland right away Kono and Tony spoke to a woman named Karen who eventually told them where Leland was at. However, Leland admitted he had only been at the location a short time which led Five-O back to Karen who was dead.
Checking Cathy’s history it turned out she was a con-artist who had a partner, the partner turned out to be Raines’ son-in-law Todd who had killed Karen because he wanted her out of his life after he fell in love for real with Raines’ daughter.