Dexter is about a guy who works for the forensics department of the Miami Police Department as a blood spatter analyst. He also happens to be a serial killer who kills only other killers. He has a strict code he operates by, instilled in him by his foster father (also a cop) - kill only those who deserve it, make sure he has solid proof that they deserve it, and don't get caught.

It is a ridiculously awesome show, and this past episode actually broke the all-time viewership record for the channel it airs on. The first season is out on DVD, but I have no idea how much that helps you in your country.