After chasing down a bounty with his team, Dog the Bounty hunter gets a jolt when the body of Dana Brown falls from the sky and lands on his SUV. Five-0 is called in to investigate, since Dana's post-fall injuries indicate that she did not jump on her own accord. Max finds an alarming amount of bruising and tissue scarring, which leads McGarrett to think that she could have been mixed up in some bad business. However, the team soon learns that Dana was actually part of a local roller derby club, the Diamond Dolls, and that most people knew her as Dicey Hot. They try to interview Dana/Dicey's teammates and head coach, Eric Blair, but none of them are particularly forthcoming. McGarrett decides that they need to get someone on the inside so that one of the girls might open up about Dicey, so Catherine is sent undercover as 'Betty Clocker' to fill Dicey's spot on the team. After taking some licks in the rink, Catherine earns the respect of the team and gradually starts to learn more about her teammates. A break in the case comes when she hacks into Coach Blair's computer to get the team roster, but instead unearths a bunch of photos of drugged Diamond Dolls in pornographic poses. McGarrett and the team quickly realize that Blair is the one who killed Dana/Dicey, and Catherine manages to subdue him before he can kill another one of the Diamond Dolls.
Meanwhile, Doris is confronted by a burglar in her home, who knocks her out and takes a box containing a microfiche detailing her entire black ops career. Catherine is forced to tell McGarrett about Mangosta, an operative from Doris' black ops past who may have resurfaced, and he's furious that she lied to him.