The Five-0 task investigate the death of a Kindergarten teacher who took a fall from a four-story building onto a parked car right in front of Dog the Bounty Hunter and his team grabbing their latest bounty. McGarrett (Alex O’Loughlin) and Danny (Scott Caan) question the victim’s boyfriend (Tim Lucason) and co-workers about her series of scrapes and bruises (all caused prior to the accident), but it takes Kono (Grace Park) finding part of a parking stub to lead Five-0 to the discovery that their victim was secretly a roller derby girl.
During the autopsy Max (Masi Oka) discovers the victim was poisoned before taking her big fall. That, and learning that the victim’s team is without a jammer for the upcoming championship, gives McGarrett the idea to send in Catherine (Michelle Borth) undercover to see what she can learn from the victim’s tight-lipped teammates much to the amusement of Danny, Cho (Daniel Dae Kim), and Kono. With a background in competitive figure skating, but a complete newbie to roller derby, Catherine is ecstatic she came in second during tryouts. Although she doesn’t make the team, she gets a second chance when the woman who beat her out coincidentally gets arrested for four unpaid parking tickets the very same day.
Suspects include a local bookie (Sven Erik Lindstrom) who was trying to convince the victim to throw the championship before her death, the jammer (Zoe Bell) of a rival team, and even members of the victim’s own team who didn’t appreciate how their coach (Drew Powell) put her on a pedestal. The real killer has a far creepier motive, and, without meaning to, Catherine’s snooping puts one of her teammates (Tiffany Dupont) in danger.
In the episode’s B-story Momma McGarrett (Christine Lahti) gets taken to the emergency room after being knocked unconscious by a burglar stealing the same mysterious toolbox she liberated a few weeks back. McGarrett’s unanswered questions and concern for his mother’s safety force Catherine to spill the beans about the recent attack on his mother’s life by a spy from her past. The tension between McGarret and Catherine is nothing compared to that of mother and son as McGarrett forces his mother to divulge the contents of the box (records of her past, and leverage against enemies who might strike against her or her family).