VERY few actors have enjoyed a career in both films and on television as successful as James Spader has.

On the big screen, Spader has played villains (Wolf; Pretty in Pink), a nerdy scientist (Stargate), men with strange fetishes (Sex, Lies and Videotape; Secretary; Crash), an assassin (Two Days in the Valley) and a giant robot (Avengers: Age of Ultron, for both voice and motion capture).

He also made his name on television as smarmy lawyer Alan Shore in two shows, The Practice and Boston Legal (he won three Emmys for this role), and currently can be seen as charismatic mystery man Raymond ‘Red’ Reddington in The Blacklist, which is already into its sixth season.

The Blacklist began with the FBI’s most wanted fugitive turning up at the bureau’s headquarters and offering to inform on dangerous criminals who fly under the radar of the authorities, in return for immunity.

In the following five seasons, viewers are kept on tenterhooks speculating on who Reddington really is, why he does what he does, and why he only wants to work with young FBI profiler Elizabeth Keen, played by Megan Boone.

As the story unfolded, more explosive secrets were revealed, including the fact that Elizabeth’s husband Tom (Ryan Eggold) was ‘hired’ by Reddington to keep an eye on her, and that Reddington could very well be her father.

There was also the matter of a mysterious bag of bones that Reddington was desperate to keep buried.

At the end of season five, viewers were left gasping when Reddington turned out not to be who he said he was – and that the real Reddington was, in fact, dead.

Season six opens with Elizabeth maintaining a facade of a relationship with Reddington, while she and her half-sister Jennifer try to find out who this man really is.

Reddington himself is facing prison and the death penalty after the Department of Justice decides that he must pay for his crimes.

In a tele-conference call with Spader in Los Angeles, the actor explains that the stakes are higher for the characters this season, and the steps Elizabeth will be taking are dire for Reddington, despite the fact that they have formed a relationship of sorts.

“You are still intrigued by the secrets of who both of them are,” he adds. “What is happening with the characters now is more compelling than the nature of their relationship in the past was.”

Reddington has always been mysterious, and with each season, the mystery that surrounds him only gets deeper.

“I have to give an enormous amount of credit to the writers of the show,” says Spader, who has just finished shooting episode 15 for season six.

“I pushed them, and they have pushed themselves to find a way to sustain the enigmatic quality of this character, and still be able to surprise and pique the audiences’ interest.”

He also likes the way the writers handled the story, occasionally putting some parts aside for a while to tell a few other stories, before returning to the main plot.

Spader enjoys the many new revelations about his character, and how the character has survived and prevailed throughout the seasons.

“I remember when I read the script of the pilot, I said to myself that this show can really turn into anything. Sure enough, that is exactly what happened.”

He adds that from the day he was shown the pilot script by John Davis and John Bokenkamp, he has been working closely with them on the storyline that would carry them to an inevitable end.

Spader describes Reddington as someone who values life because he has seen for himself how life can be taken by others – even by him on occasions. While he loves life, he also can be ruthless and scary.

Spader finds these contrasts make Reddington exciting to play.

He also likes the fact that Reddington isn’t always a step ahead of everyone else in most situations. But he maintains this facade by thinking quickly on his feet, and giving the impression that he knows the outcome.

It is this confidence, and how he operates from a position of fear, that draws Spader to the character.

“This is the kind of show that, when it comes to an end, you can watch the whole thing again with an entirely new light.”

Will Reddington remain a mystery to the end, or will the audience finally know all there is to know about him in the show’s finale?

Surprisingly, Spader thinks viewers can have both.

“I think you can know him and not know him at the same time. I think you can spend a lot of time with him and still have more that you would like to know.

“I think the way you can do that is to create someone you can never be comfortable with. And as much as you think you know him and are comfortable with him, you never lose sight that he scares you.

“I think you can end the show with a feeling of wanting and a feeling of satisfaction.”

The Blacklist airs on AXN (Astro channel 701/ 721) on Saturdays at 10.55pm.