A jacket left behind in a stolen car carries the DNA to prove who was driving the vehicle. But it takes detective work to figure out who he is - and it turns out he's responsible for a series of car thefts and has been using fake number plates to hide the vehicles. And when detectives reopen a cold-case murder, they find a witness who was too scared to speak out 30 years earlier. He provides the key evidence police need to nail the man they've always suspected.