Bernadette Peters is putting her stamp on Katy Keene.

The Broadway legend shows off her pipes in Thursday's season finale of the Riverdale spinoff, and only ET has the exclusive first look at her guest appearance.

Peters' Miss Freesia, a wealthy Upper East Sider and Pepper's mother figure who taught her everything she knows, including pulling off the classic con, takes the stage at the newly opened Pepper Plant to the delight of the crowd (and to Pepper's dismay) to sing -- what else? -- Billy Joel's hit song, "New York State of Mind," and what a glorious performance it is.

Afterward, Miss Freesia and Pepper (Julia Chan), who has just spent time in the slammer, have a little heart-to-heart. Considering Pepper's current financial and legal troubles, Miss Freesia's return to the city couldn't have come at a better time. 

"Where have you been?" Pepper desperately asks in ET's exclusive clip. "You took [Pepper Plant investor] Chad's money and you left me high and dry!" 

"Not at all. We're partners," Miss Freesia reassures Pepper. "Which is exactly what I told your landlady this morning when she tried to board this place up."

"Why would you steal from me?" Pepper asks, prompting Miss Freesia to reveal a new scheme she has her eye on. "I did it for you. I took that sad, little cash and I used it to buy my way into a much bigger payoff."

She lays out a potential new con for Pepper to take part in, which calls on them to pose as high-end leather suppliers, which could be Pepper's way out of trouble. Question is, will she take the bait? 

The season finale of Katy Keene airs Thursday, May 14 at 8 p.m. ET/PT on The CW.

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