Blair Underwood has done it all over his career. The accomplished actor racked up television credits on "L.A. Law," "In Treatment," "Dirty Sexy Money," "The New Adventures of Old Christine," "The Event" and 2013's short-lived "Ironside." His movie roles include "Deep Impact," "Set It Off" and "Rules of Engagement." As if that weren't impressive enough, Underwood snagged the lead part in 2012's Broadway revival of "A Streetcar Named Desire." However, he'd never ventured into superhero territory -- until "Marvel's Agents of S.H.I.E.L.D."

Underwood plays Dr. Andrew Garner, a highly respected Neurologist and Forensic Psychologist recruited by S.H.I.E.L.D. to evaluate super-powered individuals such as Daisy/Skye (Chloe Bennet). He was also previosuly married to Agent Melinda May (Ming-Na Wen). Last week's episode dropped a major bomb on the Marvel Cinematic Universe, revealing Andrew's dual identity as Lash, an Inhuman powerhouse serving as judge, jury and executioner to his own kind.

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Ahead of tonight's new episode, "Chaos Theory," Underwood spoke to CBR News about being kept in the dark about Andrew's split personality, tapping into classic themes, the rocky road ahead with May and the ultimate fate of Lash.

CBR News: This TV series is your first crack at superheroes and genre material in general. What turned you on to "Agents of S.H.I.E.L.D."?

Blair Underwood: Well, part of it was just that, that it's a different genre than anything I've ever been involved in. Another part was that I got a chance to work with a good friend of mine, Ming-Na Wen. We went to college together, so to be able to work with a friend in a world that's new to me is exciting. Also, my three teenagers think it's very cool. All the elements came together at once.

Going into Season Three, how much did the producers disclose about Andrew and his connection to Lash?

Coming into the season, I only knew they were going to delve more into Andrew's personal life. In the second season, I came in as an appendage to Agent May. It was really a device and a construct to open her up and see more of her life. When they extended the invitation to come back for the third season, they said, "We want to keep that and build on that, and explore who Andrew is." Boy, did they ever.

But did the creative team spill the beans upfront that Andrew was Lash?

Oh, I had no idea until Episode 4 where you think Andrew is dead at the end, in the convenience store. We had the table read for it and I'm thinking, "Maybe Andrew is dead, too." The producers -- Jed Whedon, Maurissa Tancharoen and Jeph Loeb -- said, "If you have some time, if you have a minute, let us tell you what's happening with the character." This happened to be on my birthday, which was August 25. They said, "We thought you might like to know that you are Lash." I was like, "Oh, man. That's very cool." We were about to shoot Episode 4 and then it was revealed last week in Episode 6. I did tell them it was the best birthday gift they could have given me.

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Having two separate actors play Andrew and Lash certainly helped to perpetuate the mystery behind his true identity.

Yeah, first of all, there's the fact that they established Lash in the first episode of the season. The big reveal didn't come until six episodes later. Number two, in the world we live in and the marketing aspect of it, it was revealed during Comic-Con this summer that Matthew Willig would be playing Lash. So, it's not even a thought until Episode 4, when you realized that he can transform, that he could be someone else. That's when the wheels started turning. I had friends of mine sending #AndrewisLash. I'm thinking, "I swear to you, when they broke down the story, I played the character and still had no idea." I didn't see it coming at all.

Considering Lash doesn't have a human form in the comic books, did you still bone up on his history?

I did. In fact, I went home and immediately went online and looked up the issue of "Inhuman" where Lash is introduced. That was only about two and a half years ago in the "Inhuman" series. So, yeah, I wanted to understand his origin story. I knew it was going to be different, that our show's version was going to be different than the comic-book Lash. But, I still wanted to understand what other people were bringing to the table and what they were expecting.

What kind of discussions was there about whether Andrew is experiencing some kind of Jekyll/Hyde syndrome or whether he was in full control of both personas?

I can't give too much away, but those questions will be answered in the next episode -- How it happens, when it happens, when he learned about it and how he feels about it. I can say it's all very complicated, which from an acting standpoint, it makes it compelling and intriguing to play. There's so much conflict within him.

Viewers assumed Werner and his cronies killed Andrew. How happy were you with the way that played out and that audiences were kept guessing about his fate?

I quite liked it. It's one of the things Marvel has done so well on the show. They really plot these storylines out way ahead of time. They don't always let us know. We're on a need to know basis. I did like the idea because it fuels the fire. The anticipation grows.

A few Saturdays ago, I went to Stan Lee's Comikaze convention here in Los Angeles. So I went there and so many people were coming up to me saying, "Man, I'm so sorry you're dead." I was just laughing. "Just keep watching."

Obviously, Andrew isn't simply some rampaging monster. What's his agenda? How does he view the Inhumans?

Being an Inhuman himself, Lash sees them as an exalted society and it's an honor to be an Inhuman. Not everyone is worthy of that moniker. He takes it upon himself to be judge, jury and executioner of who is worthy of being an Inhuman and who is not. I think that's where it begins. Nothing stays the same. We all have to evolve one way or another. Right now, there is very much the Dr. Jekyll/Mr.Hyde, Dr. Garner/Lash syndrome going on.

Speaking of that, one of the things that excited me the most, as soon as the producers told me that Andrew would be Lash, was Jeph Loeb said, "It's like the Hulk." I saw three classic themes and they are classic because they work. There's Dr. Jekyll/Mr.Hyde. You'll see in Episode 7, because of the love story with Agent May, there's Beauty and the Beast. Then, of course, there's the Hulk.

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Lash determines who deserves to be an Inhuman. Does that explain why he didn't finish off Daisy when he had the opportunity or is there something else going on?

There's something else there, but that's part of it. Andrew was brought in initially to evaluate Skye/Daisy/Quake. There's a very strong respect and admiration he has for her. He cares for her. When he turns into Lash, he can't necessarily control everything that's happening, that he does, which is part of the conflict and fear within him. He can't control everything, but there's most definitely a certain bond between Andrew and Daisy. Again, nothing stays the same. Right now, it may be 50/50 Andrew/Lash, but that may not stay the same; Lash might overtake Andrew or vice versa.

May learned Andrew's secret from a dying Werner. What does she do with this major piece of information?

She gets pissed. As you can imagine, May wants a lot of answers and she's well in her rights to get them.

Andrew and May clearly still harbor strong feelings for one another. How sympathetic will she be to his circumstances? Or, will she ultimately prove to be his downfall?

I don't know. What I can say is there is a great deal of confusion because you have the intellect of what is right and wrong. You see somebody you love, who is killing people. You don't understand why, but then you also have the heart involved. There's a very longstanding relationship. They used to love each other and that's what makes it so complex.

At the same time, what is Daisy and S.H.I.E.L.D.'s stance on Andrew and his cause?

That's the next episode. I can't give that away or Marvel will kill me. All of that will be explained real soon and you'll see it played out.

According to next episode's teaser trailer, Andrew seems to be getting in on the action.

Yeah, that's fair to say. I would love to do even more action. That was one of my initial conversations with the producers. I said, "Well, I'm married to May and she's always kicking ass. Does he not do any of that? Do they do it together? Do they learn together?" I was throwing my hat in the ring for that.

What else can you preview about what lies ahead for Andrew and the path he's chosen?

What Marvel has done really well, whether it's with Ward [Brett Dalton] or Andrew, is they create and present these characters that the audience gets to know and hopefully connect with in some way, shape or form. Then, they turn everything on its head. For Ward, who is a great character, he's a bad guy now. Even when they are writing him, there's a reason he's bad. That's what is interesting.

In Lash's case, while he's doing bad things, maybe they are not so bad once you understand why he does them. Maybe he's an asset. We don't know. There was a character, who was a like divining rod for Inhumans, and they found him in a closet. He said to S.H.I.E.L.D., "You need to stop worrying about Lash. You need to help Lash. He's trying to help you." You may see that kind of psychology and understanding of who he is. You are definitely going to see all sides of the argument. "Do we help this guy or do we kill this guy? Is he helping us or is he hurting us? Is he a liability or is he an asset?"

"Marvel's Agents of S.H.I.E.L.D." airs Tuesdays at 9 P.M. on ABC.