The episode opened with a US Marshall being killed in the bathroom of an airplane as it was landing in Hawaii and his suspect escaping with help from a man going by the name McGuire.
It turned out that McGuire was actually Danny’s former training officer, Rick Peterson who Danny help send to jail 10 years ago for stealing from crime scenes. Peterson picked up Grace and used her as a hostage to get Danny to meet him.
Rick takes Danny to meet Stan, and forces Danny to get a gun he has hidden close by and shoot Stan dead, stating that Rachel will never forgive him so he will lose the one thing he loves the way Rick lost his wife Kim while he was in prison.
Steve, Kono, and Chin Ho showed up just as Danny and Stan met, Danny shot Stan in the shoulder to knock him down and then fired 2 more into the ground, making Rick think he had shot him as Chin Ho and Kono came up beside the car and got Rick out.
After threatening Rick (and shooting him in the leg) Danny learned where he had hidden Grace and went and found her safe and sound in a storage locker.