Don Ellis and Kevin Long were vice detectives working as partners out of Hollywood Division as of 2015. Ellis was the senior of the two, as well as the more aggressive and intelligent. They were also corrupt cops who used their position to enrich themselves. Their primary criminal enterprise was a prostitution setup whose purpose was to ensnare and blackmail wealthy or high-profile clients. They used two prostitutes that they referred to as the Bobsey Twins. In addition, they used a transvestite prostitute, James Allen, as an off-the-books confidential informant.
In November of 2014 their blackmail enterprise snagged Dr. Schubert. They wanted $100,000 from him up front but he didn't have the cash, so they accepted jewelry which they sold to a jewelry store that didn't ask too many questions. In 2015, after Lexi Parks started making trouble, they killed her and planted DNA evidence from Da'Quan Foster which they had obtained from Allen. They started following Mickey Haller because he was Foster's defense attorney. They caused Cisco to crash his motorcycle in order to impede Haller's work, and they killed Allen so he couldn't talk. When Harry Bosch replaced Cisco they started tailing him and put a tracker on his car.
One night when they were following Bosch and Haller, Ellis encountered a homeless man sleeping on the street. Ellis brutally beat and killed him. A short time later Ellis called in a phony DUI report to the police so that they could stop Haller and arrest him. The purpose was to get access to Foster's file which was in Haller's trunk.
When Bosch went to the jewelry store, Ellis and Long became concerned and decided to kill the Nguyen brothers before they could talk. They became even more concerned when they learn that someone had come into the Hollywood station during the night and made photocopies of their mug shots from the personnel chart. When Bosch showed up at Dr. Schubert's office, they decided they must eliminate both of them. However, Bosch heard them come into the deserted building, and in the ensuing shootout Dr. Schubert was killed and Long was badly wounded.
Ellis planned to flee to Placencia, Belize, but first he killed the Bobsey twins. Then he went to Bosch's house to kill him, but Nancy Mendenhall stepped in and Killed Ellis. Altogether, Ellis and Long were responsible for ten deaths including their own.