Brittany Snow knows what lies behind the mask of the infamous assailant known as "The Carver" on FX's plastic-surgery melodrama "Nip/Tuck," whose identity will be revealed in the show's two-hour finale, airing Tuesday, Dec. 20.

But, she's not telling.

"All I can say is, you won't be disappointed," says Snow. "That's what I can say. The final episode is so brilliant. I have my friends bribing me and paying me and wanting to take me out, and I'm like, 'No, I can't even tell you, because I won't be able to explain it as good as it is.' It's amazing. I think people are going to be really impressed."

Word on the street has it that even the most ardent "Nip/Tuck" fans may not be able to guess. "It isn't [guessable]," Snow says, "but it all makes sense. It's so perfect."

Snow has had a recurring role this season as Ariel, the new girlfriend of perpetually troubled teen Matt McNamara (John C. Hensley), who was raised by plastic surgeon Dr. Sean McNamara (Dylan Walsh), but is actually the biological son of his partner and best pal, Dr. Christian Troy (Julian McMahon).

The role has been a revelation for Snow's fans, which are used to seeing her as the apple-cheeked, wholesome Meg on NBC's "American Dreams." As Ariel, the loyal daughter of a white supremacist (Brian Kerwin), Snow donned black clothes and eyeliner, sported Teutonic jewelry and spouted neo-Nazi slogans.

"It's actually the most rewarding role I've had in a while," Snow says. "This is the thing where I went to work every day just scared out of my mind, because it's so unlike me. What I found is it's actually really sad. I do feel for the character.

"It's not really her choice, it's what she's been brought up with. Ariel is trained to think this way. She loves her father so much, and she wants to do what he says. There's definitely an underlying subtext storyline of her father being abusive. She's scared that he will hurt her. The relationship is a very unhealthy one. They're so enmeshed and involved with each other that she just goes with anything he says in fear of him not loving her."

Now that the job is over, Snow hasn't held on to Ariel's viewpoints, but has kept a bit of her fashion sense.

"I took some of the black combat boots," she says. "I'm pretty preppy in real life, so it can look really cute."

Even though he tried to get Ariel help for her psychological problems in the most recent episode, Matt has often crossed moral and legal lines, even resorting to violence.

"The funny thing is," Snow says, "John is just such a great guy, and he's so unlike his character. He is such a sweetheart, the sweetest, most generous, most professional actor. Working with him was always fun and great. So to see his character, watching him on the show, was just, wow. I was blown away by him. He's very cute."

The relationship between Matt and Ariel rapidly became sexual, and that was another change for Snow.

"Considering that John and I became really good friends during the shooting, it was very easy," she says. "We just made fun of each other. By the time we had the love scenes, I knew the crew, and I was comfortable. It's really awkward, but you've got to do it. It was definitely something new for me, but it was something that I was definitely glad it was over with, when it was over."

Snow also got some advice from good pal Sophia Bush ("One Tree Hill"), who played the girlfriend of Matt's former girlfriend, Vanessa (Kate Mara). In one scene, the three ended up in bed together.

"I got advice on how to do a sex scene from Sophia," Snow says, "because she's one of my best friends. She gave me fair warning about John, saying how amazing he was. I was glad that she gave me some tips."

The role did turn a bit dangerous during a scene in which Ariel pierces Matt's ear.

"My hand caught on fire," Snow says. "I poured this water on my hand before we started, and then I had to do this weird trick with the Zippo lighter. I never knew how to do that with the Zippo, because I've never been good at lighters. I flipped it, and I guess the flame caught onto the water on my hand, and my hand was blue.

"John went, 'Holy crap!' I put it out with a blanket, but the whole crew was flipping out, because for five seconds -- which is really long if you think about it -- my hand was on fire.

"I was fine, but it was so weird."

As for what happens to Ariel in the finale, Snow says, "There really isn't a resolution. It's kind of a huge mystery. I won't let you guys know what the mystery is, but it's a big episode."

It's even possible that Ariel could return. "It depends on my schedule," Snow says, "but I'm totally willing to come back, because I love the cast and the crew. It'll be awesome."