The series is one of these new prime-time, action-packed dramas filled with twists and turns, where you find yourself rooting for the bad guy then wondering if he is actually the bad guy after all. Spader says it's hard to tell: the actors are finding out about their characters as they go along.
"He's a very bad guy who's capable I think, or has the capacity, of being good. Either that or sometimes it vacillates to being a good guy who's capable of being very bad.
"He's very enigmatic," he decides. "Somewhere along the line he went off the rails and disappeared and has lived a second life involved in international criminal activity and is still doing that, getting into a lot of trouble with his new playmates, the FBI."
Spader says what interested him about Reddington was that he's very comfortable in his own skin. "I think he relishes his life and looks upon this new strange relationship with the FBI as a brand new adventure. And I don't think it's clear as yet who's getting more out of this contentious relationship."
Reddington's puzzling relationship with his protege Lizzy Keen is what drives the drama forward. He knows secrets from her past - about her father and her husband, Tom - and Lizzy's emotions are put to the test as she swings between trusting her teacher and fearing for her life and those closest to her.
Boone says her character is very trusting and being thrust into this tense situation makes her vulnerable: "I spend most of the scenes with Red wondering what he wants from me ... Red might be a good guy, this might be a story of redemption for him," she says.
Lizzy's endeavour to reveal Red's "blacklist" of corrupt politicians, mobsters, spies and international terrorists, has made the new series one of America's top rating programmes. Fourteen million viewers tuned into last week's episode (episode 12) in the US.
With Spader in the lead, this is not unsurprising. Following his turn in the Molly Ringwald hit, Pretty in Pink, the actor became known for a string of roles in which he played dark, twisted and creepy characters: a sexual voyeur in 1989's Sex, Lives and Videotape, a car accident fetishist in Crash (1996); and a sadomasochistic spanker to Maggie Gyllenhaal's sweet and submissive assistant in 2002's Secretary. The New York Times film reviewer Janet Maslin once credited Spader with "turning the business of being despicable into a fine art".
More recently he was cast as the eccentric W.N. Bilbo in Lincoln opposite Daniel Day-Lewis. And Spader is no stranger to television, of course, having played the sardonic lawyer Alan Shore in David E. Kelley 's The Practice and Boston Legal, which won him three Emmy Awards.
Whatever the role, he knows what is needed to maintain his interest. "I just look for something that can change and has a broad landscape that you can explore for some time and that can evolve and develop and change," he says. "Something that can still surprise you way, way down the road, otherwise it becomes a tedious, redundant bore."
While television is now the medium of choice for actors seeking venerable, meaty roles, a series does have to sustain a player's curiosity for a much longer period of time than film does. "I thought when I read this script that my questions about [Reddington] would probably last and go unanswered for some time," says Spader.
"But also I saw that I would be able to bring something to it that serves it well and also serves me - that I would enjoy it and have some fun doing it. And, it's making a television show after all, so therefore there's no point in doing it unless there's some fun and games."
Speaking of such things, Spader has of course been announced to play the psychotic robot villain Ultron in Avengers: Age of Ultron, the next film in Joss Whedon's US$2.14 billion comic book franchise. It's a new genre for the 53-year-old, although playing the villain has always been his forte. Whedon has said Spader was his first and only choice for the role. "He's got that hypnotic voice that can be eerily calm and compelling, but he's also very human and humorous," Whedon says. "He's the guy to break the Avengers into pieces."
Spader is looking forward to using his wild and wonderful imagination again - after all, acting is just a continuation of child's play, he says. "I did a lot of that as a child. I built a lot of forts and secret hideaways. There was always a lot of chasing and capturing and tying one another up. I don't know if that was psychosexual or what.
"As a child I believed I might grow up to be a sword fighter or a pirate or a private detective."
I'm sure fans are pleased he chose acting. Spader won't admit to having a favourite character, but says he's sure there are plenty more out there that will feed his desires. "A script serves as fertiliser for one's imagination," he says. "And you have to let that take shape."
Who: James Spader
What: The Blacklist
Where and when: TV3, Sunday, 8.30pm
- TimeOut
