Bill immediately steals three pastries and puts them in his pocket.
He says to Jack: "See how good I am? The owner didn't see a thing."
Jack says to Bill: "That's typical of you Bill. I am going to show you an honest way to get the same result."
He goes to the owner of the bakery and says: "Give me a pastry and I will show you a magic trick."
Intrigued, the owner accepts and gives him a pastry.
Jack swallows it and asks for another one. The owner gives him another one. Then Jack swallows that one and asks for a third pastry and eats that, too.
The owner is starting to wonder where the magic trick is and asks: "So what did you do with the pastries?"
Jack replies: "Look in the Bill's back pocket!"