Although the promos for the fall finale of Grey’s Anatomy promise “nothin’ but bombshells,” it’s a comparatively quiet development that could end up having the longest-lasting impact on the ABC drama. At last, “Owen and Nathan’s relationship is starting to thaw,” Kevin McKidd tells TVLine. “They’re not fully friends again yet, but after the episode where they were with the baby [Harriet] together and that kinda stuff, they’ve just naturally started to reignite that friendship.”

In Thursday’s episode “You Haven’t Done Nothin'” (8/7c), working side by side after a building collapse further breaks the tension between the once-and-possibly-future besties. Owen even finds himself “confiding in Nathan about his concerns about Amelia and his life,” McKidd previews. “It’s a really great development to see, especially because Owen has had an axe to grind with him for so long. We’re finally beginning to get a sense of what their friendship was.”

Grey's Anatomy Season 13 Photos

And it’s all thanks to last week’s bottle episode, in which Owen conjured up visions of Megan, the beloved sister to whom his pal had been unfaithful. “Her trying to let Owen off the hook and say ‘You can let me go’ was, psychologically, so important for him,” McKidd suggests. “That’s why we’re now starting to see these initial steps in [the guys’ renewed] friendship.”

We’re also starting to see what the actor’s real-life relationship is like with co-star Martin Henderson. “We’ve gotten along great since the first day,” McKidd says, “but we had to play this me-hating-him thing. It was kind of getting to the point where I was like, ‘Why do I always have to be in a bad mood when this guy’s in the room?’ So it’s nice to be getting into an arena that plays more like the dynamic we have off camera.”

As influential as Megan was in just one installment, don’t expect her to reappear to facilitate any more male bonding — not anytime soon, anyway. Though McKidd calls Bridget Regan, who played his sib, “the coolest person,” she won’t be returning “for the time being.

“I’m not saying that that will be forever,” he hastens to add, “but for the time being, no, we will not be seeing her.”

So, Grey’s fans, what are you hoping to see in Season 13’s fall finale? Hit the comments.