'Grey's Anatomy': Can the Doctors Diagnose & Save Richard? (VIDEO)

"He is not the Richard Weber you know and love," Bailey (Chandra Wilson) warns the other doctors in the preview for the next Grey's Anatomy. "He is our number one patient."

That's right, Richard (James Pickens Jr.) is checking into the hospital in Episode 20, and it's up to the others to diagnose the 65-year-old "suffering from memory lapses and erratic behavior."

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We've seen signs earlier in the season that something's not quite right — a tremor in his hand, his destructive response to his office — but everyone got a look at the worst of it in Thursday's episode, as he declared at a medical conference that he could cure cancer, with random drawings displayed across the screen. Maggie (Kelly McCreary), Teddy (Kim Raver), and Hayes (Richard Flood) were present, while the others tuned in from home via a livestream. (Earlier, he also called Maggie "Meredith," but she thought it was just because he hadn't slept on the plane.)

Will Meredith (Ellen Pompeo) be the one to fix him? She seems to think so in the promo below.

In addition to this "tricky diagnosis," "Sing It Again" will also see Owen (Kevin McKidd) and Link (Chris Carmack) treating an older woman who can't stop singing after surgery. Plus, Tom (Greg Germann) gets help from Teddy when an estranged love one from his past shows up looking for help.

Click through the gallery above for a look at what's happening at Grey Sloan in this episode.

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Grey's Anatomy, Thursdays, 9/8c, ABC