L.A. Heat (1999) : 1x16

An abandoned church near August's home explodes into a fireball, triggered by an illegal methamphetamine lab. The next morning, he and Chase confront a group of bikers while trying to arrest one of them, and the bikers' trailer erupts into flames. It was being used as a meth lab. It's apparent somebody wants the labs out of business. Determined to crack the case, the detectives team up with Annie Mason, a new forensics assistant at police headquarters. Annie is able to turn up a suspect, a dangerous biker called the Falcon, with a rapsheet a mile long. But when he checks out the man's file, August is shocked to recognize the Falcon as Robert Hatcher, his former partner.