Cho's past life as a gang member in the Avon Park playboys is revealed when a member of the gang is murdered. Cho is heading to meet his girlfriend, Elise, for dinner when he gets a call from Oakland PD Detective Florey. Apparently the victim called Cho's cell phone multiple times over the last few weeks. Found on the victim's body is a sheet of paper containing a series of seemingly random hand-written numbers and symbols. Cho identifies the victim as David Seung, a known gang member of the Avon Park Playboys and admits they were the best of friends fifteen years ago when he was also a member of this gang. David's grandmother begs Cho to help find her grandson's killer but he turns her down. Cho makes it clear to the team that he has no interest in investigating his old friend's death but Jane persuades him otherwise. Together they seek out Jon Jon, a current member of the gang who tells them that David left the gang months ago after he left prison, moved in with his girlfriend, Christina and got a job as a janitor in Alameda. They question David's boss and owner of Alameda janitorial, George Rodriquez who tells them that David was a hard worker and never gave him any problems. He was working as a janitor at a financial office in San Francisco. Back at CBI, Rigsby tells Cho that David's girlfriend, Christina overheard David talking with someone on the phone named KS. Cho informs the team that KS is the head of the Avon Park Playboys and decides to drop this investigation because he realizes that David's death was just another gang killing. Later that evening, two masked men break into Cho's home, forcing Cho and Elise to the ground at gunpoint. After roughing up the couple, one intruder warns Cho to "Stay out of Playboy business." Now that the case has become personal, Cho and Jane return to Jon Jon and force him to tell them of KS' whereabouts. Cho finds KS who swears that he had nothing to do with David's murder. David came to him to buy five thousand dollars worth of coke, telling him it was a one time deal. The team figures out that if David wasn't using, the coke was for someone else. Focusing on David's last place of employment, the financial brokerage firm, they discover that the drugs were for executive Jeff Reed. When questioned, Reed's secretary, Amber, tells them that he caught David stealing a laptop from the office one night. Knowing that he was in a gang and had drug connections, Reed blackmailed David into getting drugs for him. Cho, Jane and Rigsby find Reed at the office. Cho gets physical with Reed and tells him he's not going to stop until Reed admits he killed David. Concerned with Cho's violent behavior, Rigsby and Jane try to stop Cho but he locks them in the office. Dragging Reed out of the office, Cho raises his gun and fires. Upstairs, Jane and Rigsby react to the gunshot as they hurry to stop Cho. Along with Jane and Cho, George Rodriquez who's covering the janitorial shift find Cho standing over Reed's body. Rigsby takes Reed's body out of the office. Jane tells Cho that Reed didn't confess so if he didn't kill David, who did? In a rage, Cho threatens to kill George unless he comes clean. George hired David because he wanted David to steal financial information for him. When George wanted David to continue stealing fro him, David threatened to turn him in. George killed him. Jane opens the door and yells to Rigsby to come out. Rigsby enter with Jeff Reed, alive. The whole shooting was a setup. Cho goes to see Grandmother Seung and tells her that he was wrong about David, he was trying to turn his life around. He asks for her forgiveness and she gives it.