Grey's Anatomy's Kevin McKidd on Cristina's Big Mistake and His "Upbeat" Episode

Grey's Anatomywill lighten up a bit when Kevin McKidd steps behind the camera for the fourth time for Thursday's episode.

Following the plane crash — which brought on the deaths of Mark (Eric Dane) and Lexie (Chyler Leigh) and the amputation of Arizona's (Jessica Capshaw) leg — Grey's kicked off its ninth season on a very dark note. But McKidd promises he's about to turn that around with what he calls an "upbeat" episode.

Grey's Anatomy Scoop: Is there hope for Cristina and Owen?

"I think the writers felt the audience needed a break, so Episode 4 is really fun," McKidd tells TVGuide.com. "All my other episodes have been quite intense, so it's been really fun to break out of that. I think people will be relieved to take a rest and just get to have fun with the show a little bit after the first few episodes."

The storylines that offer comedic relief include a patient with huge testicles, which McKidd says they had trouble shooting around. Plus: Catherine Avery (Debbie Allen) returns, which causes a rift between Jackson (Jesse Williams) and Dr. Webber (James Pickens, Jr.). "Jackson and Richard have a big standoff about the ongoing saga of him dating Catherine," McKidd teases. "Bailey [Chandra Wilson] weighs in on that."

Grey's Anatomy is a drama, however, so there will be one very large obstacle for fans of Cristina (Sandra Oh) and Owen's relationship. to get through this week. Spoiler Alert: The promos don't lie! "[Cristina] has a sexual relationship with somebody else in Minnesota," McKidd says. Dun Dun Dunnnn! Also... really? Dr. Parker (Steven Culp)? Really?!

But there is hope on the horizon: McKidd says Cristina's exploits are an "empty experience for her."
"It fulfills a certain need for her, but there's certainly not that same thing that she gets when Cristina and Owen are together," he says. "It's going to be really interesting to see how to get back and whether they're able to. They may still love each other, but there might just be too much hurt going on. There might just be too much baggage to really be able to heal or rebuild. It's a painful truth, but I think Cristina and Owen wish they could be back together, even though they're apart."

Grey's Anatomy Scoop: Jessica Capshaw discusses Arizona's fate and what's next

And don't necessarily expect Owen to retaliate against Cristina's indiscretions. "I think he's manning up to what happened," McKidd said. "He's holding out for Cristina. Whether that will be reciprocated, he doesn't know. But until he's explored every avenue to see if it's heal-able and fixable, then he's going to hold out for her because she's the love of his life."

This is exactly why, McKidd believes, executive producer Shonda Rhimes has dubbed this the season of romance. "It's like that old phrase: The darkest hour is always before the dawn." Can the sun rise now, please?

Grey's Anatomy airs Thursdays at 9/8c on ABC.