Dexter is a show about a sociopath cop who is a vigilante. He is a blood stain expert who has a serial killer stalking him as well.
The show deals with his mental illness, and displays all of the energy he must evoke in order to act normal. The back story is that his father was a good cop who adopted him, and taught him how to channel his sociopathic tendencies.
The summary does it no justice. It is an incredible show.