What is hidden in 3D image?

A man takes his place in the theater, but his seat is too far from the stage.
He whispers to the usher, "This is a mystery, and I have to watch a mystery close up. Get me a better seat, and I'll give you a handsome tip."
The usher moves him into the second row, and the man hands the usher a quarter.
The usher looks at the quarter, leans over and whispers, "The wife did it."