Penny's sister Shannon was found dead in her car at the bottom of a cliff more than five years ago, and her death was ruled a homicide. The case remains unsolved. Now Penny is accusing her father of being involved in his own daughter’s death, an accusation her father vehemently denies.
"I know you have paid someone to kill Shannon. Don't sit there and act like you're so innocent," she says in the video above.
Why is she choosing to air her accusation on national TV? Watch more here, and see the entire episode of Dr. Phil on Thursday.