Then you have to fill the hole.
You make the fill by creating a "clean plate" or by filming one at the time of production.
If you have no Idea what these terms mean then as Todd said in his fisrt post to the first time you asked this question, start with the basics.
Reminds me of a conversation I had with a coworker. She brings me video footage of her child's soccer game. Her girl kicked the wining goal but there is another soccer mother standing in front of her camera. "I need to see my girl's goal. It's digital, you can edit that lady out, right?"