SPOILER ALERT

The Season 17 premiere of "Grey's Anatomy" brought on a rollercoaster of emotions for viewers with one of its most jaw-dropping plot twists ever: the return of Patrick Dempsey's character, Dr. Derek Shepherd.

It's a character resurgence fans of the medical drama never saw coming. Shepherd, who was married to Ellen Pompeo's Dr. Meredith Grey, died in a 2015 episode.

The two-hour premiere showed the doctors at Grey Sloan Memorial battling a beast they've never taken on before in the emergency room -- the coronavirus pandemic -- and Pompeo's character was overcome with heartbreak as she witnessed several of her patients die alone, away from loved ones, due to COVID-19 complications.

The episode took an even more devastating turn when Grey herself was found by a co-worker passed out in the hospital's parking lot. Next thing viewers saw was Pompeo's character strolling down a beach and locking eyes with her late husband, known to viewers as "McDreamy."

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"Derek, I miss you," Pompeo shouts to Dempsey's Shepherd, to which he replies, "I know."

Several questioned what this meant for Grey's character. Was she in heaven reuniting with the love of her life once again, or was it all just a dream? 

A teaser for next week's episode shows Grey as a patient herself, with her colleagues warning her that her symptoms may get worse. Hundreds of fans took to social media, pleading for answers in real time. But it was the scene featuring Dempsey and Pompeo's reunion that they fawned over.

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"You how much I miss you @PatrickDempsey how could you do this to me My heart is melting #mcdreamy," one viewer tweeted.

"i had the weirdest dream. @EllenPompeo and @PatrickDempsey were hanging out at a beach and then they displayed that scene on greys as a merder endgame. if felt so real and perfect. I can't believe it," another wrote.

One fan shared behind-the-scenes photos posted to showrunner Krista Vernoff's Twitter account of the stars reuniting.

"YALL I AM COMPLETELY OBSESSED WITH PATRICK DEMPSEY, HE TRULY IS THE LOVE OF MY LIFE, I CAN'T BELIEVE THIS JUST HAPPENED I' FOR REAL CRYING AND FREAKING OUT," a third reacted.

"I just turned @GreysABC on for the first time in a few years. Thank you @KristaVernoff @PatrickDempsey @EllenPompeo This is what has been missing. These two characters that cannot be replaced. Spin a great story and make Derek real at some point in the future," another wrote to Vernoff.

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Another claimed the return of Dempsey's character "saved 2020."

"omg what's happening this is alot of emotions in a 2hour episode," the person continued. "I cried so much."

Another said they were "SO FREAKING SHOCKED."

"The way Patrick Dempsey continues to carry the show, even five years later #GreysAnatomy," quipped one person.

Another agreed it had been "5 long years" without Dempsey.

ELLEN POMPEO DISCUSSES POSSIBILITY OF CORONAVIRUS-THEMED 'GREY'S ANATOMY' EPISODE

Back in April, shortly after the COVID-19 pandemic surged around the world, Pompeo hinted that there would be a coronavirus-themed episode in the new season.

Ellen Pompeo as Dr. Meredith Grey in "Grey's Anatomy"

Ellen Pompeo as Dr. Meredith Grey in "Grey's Anatomy" (Getty)

"I thought about it," Pompeo revealed to Variety when asked if the coronavirus would spawn a new storyline for the series. "Obviously, we don't want to get too political here, but I was just watching the news and I saw a clip of Barack Obama in 2014, saying that a pandemic was inevitable and that we should be prepared for it."

The 50-year-old actress, who at times is mistaken for an actual doctor due to her longevity on the show, also applauded medical workers on the front lines at the start of the health crisis.

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"This is just from me and my family to all of you to say thank you, we appreciate you, we love you. Stay safe. Nurses rock. Doctors rock and anyone who works in a hospital or the healthcare industry, you rock," Pompeo said in a video posted to her Instagram account in mid-March.

Season 17 of "Grey's Anatomy" airs on ABC on Thursdays at 9 p.m. ET.