Rabbi Noah Muroff, a high school teacher at a private Jewish school in New Haven, discovered the money while dismantling the $150 desk to move it through a narrow doorway.
"The desk did not fit ... by just a fraction of an inch," Muroff said.
He said he unhooked file cabinet drawers and removed the top of the desk. Then came the unexpected surprise.
"Without detaching the desk, Muroff said, "this money, which was behind the drawers, was totally inaccessible."
The rabbi and his wife, Esther, were in total shock.
"We were looking at each other and laughing," he said. "This kind of thing only happens in the movies."
On the evening of September 2, just days before Rosh Hashanah, the Jewish New Year, Muroff and a friend picked up the desk from a woman, Patty, who lives just outside of New Haven. Muroff declined to identify the owner further.
"I knew this was her money," he said. "She told me she bought the desk from Staples and put it together herself."
Within 20 minutes of finding the money, around 11:30 p.m. that same evening, Muroff called Patty.
"She was speechless, without words," he said.
Muroff said the former owner told him she put her inheritance in the desk and after a while forgot it was there.
"I do not think there are too many people in this world that would have done what you did by calling me," Patty wrote in a thank you note to Muroff that CNN obtained.
The couple took their four children with them to return the money the next day, hoping their good deed will send "the message of honesty and integrity," he said.