XIII, or Thirteen, grew out of a French graphic novel, became a video game, then a mini-series and is now a popular Canadian-made TV series. The lead actor, Irishman Stuart Townsend, caught up with the XIII phenomenon when a script for the series was sent to him.
"I was like 'Wow, I love this'," he said by phone from Toronto, where he is shooting the second series of XIII. "There is action, beautiful girls and a great storyline about a guy who does not know his identity.
"He is an outsider to everything. He wakes up and is given a mission to go and steal something from a bank vault. I try to imagine myself in that situation, it would be quite a life to live.
"You know you were lethally trained but you don't know if that was a good thing or a bad thing. You don't know if you are good or bad."
Townsend's only clue to his identity is the number XIII tattooed on his shoulder. As the series, now on FX channel, proceeds he realises that he has been rescued by the brother of assassinated US president Ann Sheridan.
Both Wally Sheridan and the current President Ben Carrington want him to track down a piece of software capable of accessing all technology. And there is also the question of who assassinated Ann Sheridan.
It is a convoluted story which has a loyal following and Townsend promises viewers surprises in series two, written by Roger Avery. "It is still a spy drama but it has opened up a little more," he said.
Knowing how to box has been useful for Townsend, who finds himself fighting a lot in XIII.
"I grew up in Ireland and that is a good way to learn how to fight," he laughed.
"I did boxing as a kid and then, as a teenager, I took it out on to the streets.
"Knowing how to fight has been really helpful in the role and I've also done kick- boxing and things like that. This year, I decided to try CrossFit, which is like navy SEAL training and a real torture regime.
"But I have to say these things help because the fighting hurts. When you pull a punch you jar everything."
He no longer lives in Ireland and doubts he ever will again. He prefers being a gypsy and moving where work takes him.
He had a 10-year relationship with Charlize Theron before they parted in 2010.
XIII airs Sunday at 6.30pm on FX.