Go Set A Watchmanand To Kill A Mockingbirdauthor Harper Lee might have a third novel waiting in the wings. At least that’s what an attorney for the 89-year-old shared last week.

Attorney Tonja Carter discovered Go Set A Watchman in a safe deposit box about a year ago. She hinted there may be another manuscript as well after returning to the safe deposit box just last week to see if there were any “other things hiding in plain sight.”

“What we found was extraordinary and surprised even me,” Carter writes in a piece for theWall Street Journal. “Remember the partially opened mailer from Lippincott that the publisher had sent to Alice Lee in 1961? Well, my colleague very carefully removed its contents, which were about 300 pages of typed manuscript. It was clear to us that what was in the package had not been removed since it was first mailed.”

Will the racism of Atticus Finch in "Go Set a Watchman" alter Harper Lee's legacy? http://t.co/pcsj0PZD6S pic.twitter.com/ke1ns7TqHq

— The New York Times (@nytimes) July 12, 2015

Carter reports finding both Go Set A Watchmanand To Kill A Mockingbird sitting “underneath a stack of a significant number of pages of another typed text.”

“Was it an earlier draft of Watchman, or of Mockingbird, or even, as early correspondence indicates it might be, a third book bridging the two? I don’t know,” she writes.

Have you readTo Kill A Mockingbirdby Harper Lee? What’s your take on Atticus Finch?

10 most beautiful lines from Harper Lee's 'Go Set A Watchman': http://t.co/tTUy7huFrT pic.twitter.com/OhNJ1TQK7n

— Entertainment Weekly (@EW) July 13, 2015

Go Set A Watchmangoes on sale Tuesday. It is expected to be an instant best-seller.