The "Grey's Anatomy" Season 12 Winter finale churned up tension between newcomer Nathan Riggs and Owen Hunt, but recent spoilers foreshadow a long rivalry between the two when the series returns in February.

On Thursday, actor Martin Henderson spoke to TVLine about the revelation of Owen having a sister, and his theories on the feud between the two doctors.

"What I do know is that Owen is extremely resentful of [Riggs] being around because of something that happened involving his sister a while ago," said Henderson.

"And what I can glean from the episodes we have shot since [the fall finale] is that in a previous time Owen and Riggs were actually quite close. And this situation that happened with his sister has caused this rift that Owen refuses to forgive him for. And it seems like my character feels quite vindicated, in the sense that he doesn't feel that he has to explain himself."

Reportedly, things will continue to escalate between the pair for quite some time.

"I think Riggs understands Owen's position and is willing to allow [this tension] to exist as long as he can do his job," he continued. "But eventually Owen's strong position on it causes other people in the hospital to distrust Riggs and marginalize him to the point where it's starts to affect his ability to do his job. And that's when [the feud] escalates. That's down the line a little bit of it."

The timing, then, seems just right for a new therapist to join the fray. According to Spoilers Guide, the series will introduce an "easy, funny, kind, fatherly" therapist in episode 10 of Season 12, portrayed by Bill Smitrovich.

Could he help counsel Owen?

"All I'll say is it's life and death," said Kevin McKidd regarding Owen's feud with Riggs to EW. "It's a life and death thing."