In one sense, Thursday’s Grey’s Anatomy (8/7c, ABC) will feel less like a regular episode of the series that we all know and love, and more like a standalone movie, says Kevin McKidd, who not only plays Owen but directed the hour. “Since most of it takes place in the courthouse, it’s kind of like a really wonderful courtroom drama, like Kramer vs. Kramer.”

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In another sense, “Mama Tried” will probably feel a whole lot like classic Grey’s, since the stakes are as high as they’ve ever been in the OR. As McKidd notes, in fighting for custody of daughter Sofia, “Callie and Arizona are fighting for their lives, in a sense.” Here, he previews for TVLine “the very emotional and heart-wrenching” installment that will decide the fates of Sofia and her mothers… and possibly Penny, too.

TVLINE | What was the mood on the set like while working on this episode?

Intense. It was intense to shoot, and I think it’s going to be really intense to watch. I think people are going to really respond to it. It’s very emotional, very powerful. I mean, to fight over the custody of a child, for a parent, is probably one of the most [difficult] things they could have to do. Plus, the audience loves Callie. The audience loves Arizona. We want them both to be okay.

TVLINE | And obviously, they can’t both come out of this okay. Even their friends can’t, right?

Yeah, that’s the hard thing for all [the rest] of our characters. We’re all asked to give testimony for the person we believe should have custody. It’s really tough when you have to pick a side like that, and that’s part of the reason why it’s such an intense episode. Everybody gets cross-examined, and some people do better under that pressure than others. It really puts Callie and Penny’s relationship to the test when Penny testifies, and affects their relationship going forward in a big way. The testimony that Penny gives… she does her best for Callie, but it doesn’t go as planned, and that causes problems.

TVLINE | Is there ever a moment when Callie and Arizona are like, “What are we doing? Let’s work this out”?

They do try to connect at a certain point, but the lawyers get in there and do their lawyering thing and cause damage, so [the ex-wives’] interaction is very charged. There are a lot of hurt feelings. They try to stay civil, but it’s hard when things get thrown at you by a lawyer. Arizona especially, I think, really feels hard done in the courtroom.

TVLINE | Is there any sign, any hint at all, of the love that they used to feel for each other?

There is. They both in a way come to a point where they can acknowledge the relationship that existed. In spite of the hurt feelings, they try to reach a higher ground and respect the [past]. But it’s hard when there are hurt feelings in the heat of the moment to really follow through on that.

TVLINE | And when the heat of the moment has cooled?

After this episode, the aftermath plays out in a really interesting way in the lead-up to the finale. It gets pretty hairy in this episode. There is animosity. It’s not all fluffy and pretty and nice. There are really intense, complicated emotions flying around. But there’s a really beautiful payoff in the finale connected to this.

So, who are you hoping will wind up with custody of Sofia? And do you think Callie and Penny’s relationship can bounce back? Hit the comments!