21. License to Kill/The Tell-Tale Mark/The Supermarket Mystery

A quarter of a century after the murders of two nurses, Canadian police suspect that a former Toronto cop committed the crimes. A blow to the head of a garbage collector in San Jose leaves strange markings, and decades later a detective, with help from forensic science, matches the markings to the etchings of a vintage bar sign. California police hope that DNA will help them track down the man who stabbed and killed a woman as she sat in her parked car in front of a supermarket in 1985.