A little girl says to her mother: "Mummy, when you were away at work a strange lady came around"...
"Not now," says Mummy. "Wait until Daddy gets home."
So they wait until Daddy gets home, and then Mummy says "Now dear, what were you saying about Daddy and the strange lady?"
And Daddy starts to say something but Mummy says, "You keep quiet - I'll be talking to my attorney in the morning. Carry on, dear."
"Well," says the little girl, "Daddy told me to stay downstairs while they went upstairs, but I followed them without Daddy seeing me, and I saw them hugging and kissing at the top of the stairs. Then they went into your bedroom and shut the door, but I went up and looked through the keyhole."
"Clever girl," purrs Mummy. "What could you see through the keyhole?"
"I saw them hugging and kissing some more, and then they started to take each other's clothes off, and they carried on until they had nothing on, and then the lady got on the bed and Daddy got on top of her."
"Yes?" says Mummy. "And then what happened?"
"Then they did what you and Uncle Jack did when Daddy was in Vancouver last year," says the little girl confidently.