Staring intently into her eyes, he lunges forward and grabs her, kissing her long and hard. Unlocking his lips from hers, he caresses her face, smiles and then purposefully goes back in for another soulful smooch.…

"Cut!" someone yells, and Justin Chambers and Elizabeth Reaser separate and come up for air.

The two actors are shooting their characters' romantic reunion, which takes place this week on Grey's Anatomy. Last season, fans were left in the lurch when intern Alex Karev didn't hook up with Rebecca, the amnesiac ferry-crash victim he named "Ava" and nursed back to health. But in this Halloween episode (titled "Haunt You Every Day"), a fully recovered Ava makes a surprise return and will — at long last — seal the deal with Alex.

As with all on-screen love scenes, things are not quite as they seem. There are shadows to avoid, camera angles to be aware of, and a height difference of about 8 inches between the two actors to keep in mind. And although both actors have brushed their teeth and sucked on many Altoids, there are also matters of taste to consider.

"You do not want to make it dirty, sloppy or tongue-y," Chambers, 37, says sagely. "It's not porno." "It's not?" Reaser asks, laughing. "No, it's not. You don't want to get too crazy. It's soft porn."

The conversation may be a bit racy, but then again, we are in the halls of Seattle Grace, a hospital where the term "examination room" takes on a whole new meaning. Reaser, 32, who was Emmy-nominated for her heartbreaking performance last season, seems thrilled to slip back into character. "Ava has returned to see Alex," she says, using, as everyone around here does, her character's faux name. "She can't help herself — which is a pretty bold move, considering where we left off."

Let's review: After pulling the battered-beyond-recognition "Ava" from the debris of the ferry disaster, Alex helped deliver her baby and pick out her new face — and he displayed a surprisingly sweet bedside manner all the while. But just when it looked like they were about to get together, she remembered that her name was Rebecca and that she had a husband. Awkward! She seemed ready to end her marriage, but Alex held back even after she threw down an ultimatum. (Reaser's take: "I said, 'Give me a reason to stay!' and he wouldn't, so I had to go back to my husband.") What she didn't know was that Alex realized his mistake and ran out of Cristina's wedding to find her, only to discover she was gone. Oops, they didn't do it again.

For more on Grey's newest couple, pick up the new issue of TV Guide, on sale now.