The movie flashes forward to present day. Jacob (Steven Seagal) has become a detective in the many years since his twin's death. I guess the maker of the movie couldn't decide which villain to use, so they put both of their options in. First there's a yet unidentified serial killer who uses the zodiac and his own weird ideas to choose his victims. Jacob has to sort out the encrypted messages that the killer is leaving behind to catch him. Sounds like the plot of many existing movies, right?
Well, just to make sure we realize that Jacob is this super detective, there's also a blast from his past coming back to haunt him. Years ago Jacob caught Billy Joel Hill (Mark Collie), but due to the "excessive force" used, Hill wasn't ever even convicted. Now in the midst of searching for the serial killer, Jacob is going to have to also deal with Hill's return to society and his thirst for vengeance at the man who tried to put him away. There is no connection between Hill and the serial killer, though. There's really no reason for Hill to be in the movie other than to provide filler.
Most of the movie is filler, actually. The plot really makes little sense. I think they were going for "we put in so much violence, blood, guts, and guns that we hoped you wouldn't notice the plot." The fight scenes were exceptionally long, but we liked the way they were cut. They chopped the frames up and jumped around a lot, almost giving it a comic book feel. Maybe they did it that way to make him look like he was moving fast for a man of any age, much less his age, but it worked for the movie. It did get a little repetitive at times, though. Seeing the same shot from 5 different angles needed to be cut back some, but once again, it felt like they were filling time. I did laugh when he called a "shots fired" in. That was a little bit of an understatement since there had probably been over 100 shots fired. Jacob's method is to just punch or shoot everything until you hit the target.
If you like your movies with lots of violence and not much plot, you'll enjoy Kill Switch. Just drink enough before you watch it and you might not even notice or care that you have no clue what's going on. That's the only way I would recommend watching Kill Switch.