[Warning: The following contains spoilers for the latest episode of Prodigal Son, "Scheherazade." Read at your own risk!]

Monday's new episode of Prodigal Son, titled "Scheherazade," brought a new big baddie into the picture for the final stretch of the first season. Nicholas Endicott (portrayed by guest star Dermot Mulroney) is a longtime acquaintance of the Whitly family who's known Jessica (Bellamy Young) since long before Martin's (Michael Sheen) crimes came to light. In the episode, he initially seems charming and is one of the few New York socialites willing to welcome Jessica back into the swanky scene without making derogatory comments about her sordid family history. However, it looks like the reason he doesn't judge the Whitlys is that he, too, has some dark secrets buried... and they may be on the brink of being revealed.

The crime of the day has Malcolm (Tom Payne), Gil (Lou Diamond Phillips), and the rest of the Major Crimes Unit try to figure out who's responsible for the murder of a prominent ballet dancer with an unusual past — and, as fate would have it, something of an art world connection to Nicholas Endicott. Meanwhile, Eve (Molly Griggs) confronts Martin about the whereabouts of her sister, and he eventually tells her that he did indeed have her sister Sophie, aka the girl in the box, trapped in his home and was ready to kill her until she talked her way out of it. To escape Martin's clutches, Sophie asked for just an hour of his time to talk about people who were much worse than a simple serial killer like him. While we don't know exactly what she told him, we do know it was bad enough that he decided to cut her loose, and it was something about Nicholas.

Of course, Martin Whitly, a serial killer who's basically lied to everyone in his life by now, is not the most reliable source of any kind of information. So, TV Guide caught up with Dermot Mulroney himself to find out what is going on with Nicholas Endicott and what we can expect from him after that stunning introduction. Turns out, this newcomer to the series is going to be the tie that binds many serial killer cases we've seen throughout Prodigal Son so far.

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First of all, is there any chance Martin is lying about Nicholas Endicott right now? Obviously, Nicholas and Jessica are getting close, and no matter what the relationship between Martin and Jessica is, he's controlling of his family.
Dermot Mulroney: Oh, he could be lying. That's absolutely true. That would be only because of what a wonderful actor it is playing Martin that you'd be led to think he's playing [with you]. Everyone who is playing these roles, they're so crafty with their lines so that you can be misled. Yeah, look at how they do that.

So, what was it like to read that your character would be so evil that it could be intimidating to even The Surgeon?
Mulroney
: I thought that was going to be great, and it turns out the storyline that they came up with is way more — I only read that first script, right when they offered, I didn't hesitate for a second. Then I saw this cast. So, I took the part, and then I saw a couple of episodes, so that made me even more excited when I realized they were really onto something. It's sort of like their creepy, posh tone and weird, psychological humor — yeah, they've had some really cool stuff on this show, and it all comes to pitch in the end of this first season. It is really fun to play.

Going past this episode, now that we know what we know about Nicholas, what can you tease about what's ahead for him?
Mulroney
: You will see that Nicholas Endicott, even though the character's introduced later in the season — you've already seen several series of uniquely bad guys and serial killers — that they pack in a lot, you learn pretty quickly that he has a lot to do with everything. And they weave my character into almost each of the other characters. It's quite ingenious, really, the storyline. There's a lot yet to come.

Is this character a serial killer? Is he a human trafficker? Is there anything you can tell us about what his motivation is?
Mulroney
: Ultimately, as is with much of the show, there's always that rich, privilege, and power of course, but ultimately the theme ... his empire, I don't know how to describe it. But he is really, really bad. That may be giving away too much to say that. You are definitely in the right place right now if you are completely suspicious of Nicholas Endicott's approach.

You said that the character will relate back to some of the serial killers we've seen in the past. Does that include the Junkyard killer and going back to the pilot, the copycat killer, or is there someone specific?
Mulroney
: Yeah. I can say that there are a number of people under Nicholas Endicott's control, and they go from the lowliest gun-for-hire assassin to the upper echelons of the Manhattan elite.

Prodigal Son airs Mondays at 9/8c on Fox.

Dermot Mulroney, <em>Prodigal Son</em>Dermot Mulroney, Prodigal Son