Hill Street Blues is one of the premier achievements of narrative television, and this episode is in my opinion one of the ten best they ever did. (It's currently the highest ranked episode of the show on IMDb, so I'm not alone in appreciating it). It gives us a villain scarier than around which many movies (without the codes and practices restrictions of network TV) are built, along with many of the usual Hill Street ingredients such as ironic humour, surprise, action and emotion. Like with many episodes, you get the most out of it if you're familiar with the characters and their histories - i.e. if you've been watching previous episodes. However, this is structured so you get a pretty good payoff watching it in isolation, too. Very highly recommended, and one that springs to mind easily years after I first saw it.