Tempers flare in exclusive look at 1st scene from 'Grey's Anatomy' season 21: Watch

"Grey's Anatomy" season 21 is finally here, and "Good Morning America" gave fans an exclusive preview of the new season Thursday morning.

The dramatic opening scene of the season's first episode, which airs Thursday night on ABC, will leave fans waiting anxiously for the plot to unfold.

The new season picks up in the aftermath of the season 20 finale, with Catherine Fox (Debbie Allen) trading barbs with Miranda Bailey (Chandra Wilson), who is standing up for the interns.

"I can have all of you replaced by tomorrow," Catherine tells the group.

"What about me? Can you replace me?" Miranda says as she walks into the scene.

Catherine stands her ground, saying, "Do you know how many doctors I have replaced in my career? Your rejects can stay, but your salary will pay for the lawyers who will fix their mistakes. You're done here, Dr. Bailey. Goodbye."

Miranda isn't going without a fight, though, as she tells the boss, "I refuse to allow my job to be taken by someone who only operates on spite and greed. You don't see faces, you see dollars."

Catherine retorts that Miranda's leadership is costing her money, and the scene ends with Miranda reminding Catherine that "this profession is a calling -- not a business."

A synopsis for the episode, which is titled "If Walls Could Talk," teases more drama ahead for our favorite TV doctors.

"After firing some of Grey Sloan's best, Catherine continues to interfere with Meredith and Amelia's research. Accidents at a climate change protest bring unique cases to the hospital, and Bailey encounters a blast from the past," the synopsis reads.

This season will also see the return of Kali Rocha as Sydney Heron and Jesse Williams as Catherine's son Jackson Avery.

"Grey's Anatomy" season 21 premieres Thursday, Sept. 26, at 10 p.m. ET on ABC.