A ruthless home invasion gang brutally attacks a Chinese family, killing the father. This is the seventh in a string of attacks. Nash and the SIU are confused since home invasions are a Vietnamese phenomenon and they rarely cross cultural or ethnic lines.

After a nearly 20-year absence, the notorious San Francisco serial killer, ""Zodiac,"" returns to taunt Nash as well as haunt Nash's mentor (who has since retired). But is it the actual Zodiac, or just a lethal copycat? Meanwhile, Joe goes undercover as a bike messenger to nab a free-wheeling drug dealer.

Nash and the SIU uncover a counterfeitering group where the money is top-of-the-line Supernote quality. Moving in to bust the group, they discover a fake SIU gang impersonating the police. Cooperation becomes tense as suspicions abound over who and what to trust. In the interim, as Nick gets in over his head financially with his horse costs, Nash reluctantly agrees to work with Joe on an off-duty case searching for a Super Bowl ring. However, Nash and Joe soon find themselves impersonating a gay couple as the case develops differently than Nash anticipated.