McKidd, who plays Owen, told TV Line that the episode will not be as dramatic as the season six finale.
"There's not going to be some massive event, like a shooting," he said. "But there's definitely going to be a lot of things that come to light that are going to change a lot of perceptions and pose a lot of very difficult questions for people."
He added: "It's going to leave big question marks, [because] quite serious kind of things happen in the last couple of episodes that are left unresolved."
McKidd, who has previously revealed that Owen and Cristina (Sandra Oh) will face problems in the future, suggested that their relationship could come under strain in the finale.
"[Owen needs Cristina] to realise that maybe there's more to life than just work," he teased. "And that is going to play out in a very interesting way towards the end of the season."
Grey's Anatomy returns for a new episode on Thursday at 9/8c on ABC.
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