Julie McNiven Julie McNiven

This week on the CW's Supernatural (Thursdays at 9 pm/ET), a religious young woman named Anna is wanted dead by the angels, yet wanted alive by the demons of hell. Say what?! Guest-star Julie McNiven — whom you might recognize as Pete's gal Friday, Hildy, on Mad Men — shares a look at how her mild-mannered character gets caught in the middle of a most unholy war.

TVGuide.com: Anna can hear the voices of angels. How is it that Sam and Dean learn of her existence?
Julie McNiven:
Ruby finds out about me — I don't know if she reveals her source — and then tells Sam and Dean about this girl who can hear angels' conversations. I'm locked up in a mental institution because, obviously, people think I'm insane.

TVGuide.com: How does Anna know that it's angels she's hearing?
Because their conversations are all about the war that's brewing between Heaven and Hell, between the angel soldiers and the demon soldiers. When she hears about how Lucifer will bring the apocalypse ... Well, that attracts the boys' interest.

TVGuide.com: It also draws the interest of a demon named Alistair.
Yeah, and he's a big-time demon with greater powers than Ruby has.

TVGuide.com: He wants to take you to Hell for an "interrogation"....
Where they can torture me as much as they need to because I'm human. It's a scary thing having the angels want me dead and the demons wanting me alive. Either way, I'm kind of screwed!

TVGuide.com: Do angels Castiel and Uriel make their intentions clear, or is their agenda sort of sprung on Anna?
In my first episode [of two], they just come out and say it. That's when you realize I'm stuck in the middle of a horrible situation. Of course, Sam and Dean are then stuck in the middle, too, so they try to find us a way out of it.

TVGuide.com: Does one of the brothers take a greater interest in Anna than the other? Because Dean is perhaps the more romantically available one....
[Laughs] Sam actually is very protective of Anna, more than Dean I think, so every time there is some sort of fight, I get thrown in a closet or the room next door. Meanwhile, I, Julie, am like, "I want to fight!"

TVGuide.com: There's a spoiler out there that one of the brothers gets shirtless soon, and for the purpose of getting busy. But I'm gathering here that it's not for Anna's benefit.
Yeah, well... You'll just have to watch!

TVGuide.com: This is where I usually invite the guest-star to confirm what fine men Jensen Ackles and Jared Padalecki are.
Absolutely - both complete gentlemen! I had such fun working with them, and with Genevieve [Cortese, Ruby], too. The boys were hilarious.  They can go from joking around to right in a scene, but I get the giggles, so I literally had to bite my cheek and tongue to focus.

TVGuide.com: Was Genevieve happy to have another gal on the set?
She was really excited, and we got along well. We're a lot alike in our personal lives, so I found a good friend in her.

TVGuide.com: I take it that Supernatural offered you a "slightly" different experience than secretarying at Sterling Cooper?
[Laughs] Uh, yeah. Definitely. It was nice because for me as an actress still at an early stage in her career, I felt like I could really bite into this role. I was given an arc with a beginning, middle and an end.

TVGuide.com: Plus, you got out of those stuffy 1960s Mad Men clothes.
No, I actually love wearing those! Give me a girdle and I'm happy.