This is the 55th episode of C.O.P.S.
"The Big Boss never misses an opportunity for crime. He found a surprising opportunity when Officer Sundown couldn't remember he was a cop. That's when Big Boss tried to pull a robbery Empire City would never forget!"
While trying to go on vacation and after a failed arrest, Sundown gets bonked on the head and loses his memory. Big Boss takes advantage of Sundown's dilemma and comes up with a plan to use Sundown as a coach to train the crooks for an armored car robbery.