'Grey's Anatomy' boss on Meredith's COVID battle, more Patrick Dempsey appearances

There's a rough road ahead for Meredith Grey (Ellen Pompeo) in her personal fight against COVID-19 -- but now we know that will include more Derek Shepherd (Patrick Dempsey).

"Grey's Anatomy" showrunner Krista Vernoff appeared on "Good Morning America" Friday and revealed we can expect two more appearances from Dempsey this season. As for when those will happen, fans will have to tune in to find out.

Vernoff did say keeping Dempsey's shocking return -- which left fans on a cliffhanger at the end of last week's season 17 premiere and continued in last night's episode -- was "the toughest" secret she has ever had to keep.

"It was a really stressful thing, and then it was a really beautiful group effort, and then it paid off and I can't believe it," Vernoff recalled. "I was in tears."

The McSteamy reunion happens in a dream while Meredith battles COVID-19. As the titular character arrives on a beach, she comes face to face with her late husband, who died at the end of season 11.

"It's just a beautiful nostalgia," Vernoff added. "And for those of us who have lost people -- like, real people in our lives -- this gave them room to grieve again or to not grieve again or to feel joy again."

The TV show's boss said it was the doctors who advise them behind the scenes who convinced her it was important to cover COVID-19 because it's "the story of our lifetime and it's changing us and changing health care permanently." And, as Pompeo puts it, they talked about "COVID dreams and how vivid they are and how incredible they are," inspiring Meredith's journey.

"We watch these characters for years and we fall in love with them," Vernoff explained. "And when something like this happens to them, we feel it and it might change our hearts and it might change our minds. I feel like, for me, that's as good as it gets."

While fans can rest assured that they haven't seen the last from Derek this season, the preview for the next episode teases that someone else from Meredith's past will be visiting her in this dream world, so the nostalgia trip is far from over.

"Grey's Anatomy" returns Thursday, Dec. 3, at 9 p.m. ET on ABC. Disney is the parent company of ABC News and "Good Morning America."