"One Million Bucks" joke

An Elderly couple was celebrating their sixtieth anniversary. The couple had married as childhood sweethearts and had moved back to their old neighborhood after they retired. Holding hands they walked back to their old school. It was not locked, so they entered, and found the old desk they'd shared, where Joe had carved: I love you, Nancy.
On their way back home, a bag of money fell out of an armored car, practically landing at their feet. Nancy quickly picked it up, but not sure what to do with it, they took it home. There, she counted the money-one million bucks.
Joe said, "We've got to give it back."
Nancy said, "Finders keepers."
She put the money back in the bag and hid it in their attic. The next day, two Inspectors were canvassing the neighborhood looking for the money, and knocked on the door.
"Pardon me, but did either of you find a bag that fell out of an armored car yesterday?"
Nancy said, "No."
Joe said, "She's lying. She hid it up in the attic."
Nancy said, "Don't believe him, he's getting senile."
The agents turn to Joe and began to question him.
One says, "Tell us the story from the beginning." Joe said, "Well, when Nancy and I were walking home from school yesterday... "
The first Inspector turns to his partner and says, "We're outta here."