Zac and Melissa Gusé say Zac’s daughter, Karlie, vanished from their home in rural Mono County, California in the early morning hours of October 13, 2018.

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The couple says that authorities searched their neighborhood and the nearby desert for days and interviewed witnesses who claimed to have seen a girl fitting Karlie’s description, but the teenager remains missing.

WATCH Why The Mother Of A Missing Teenager Says She Believes Her Daughter Died Of A Drug Overdose

Both Melissa and Zac claim they have no idea where Karlie is, or where she could have gone to, and say they believe someone may have taken their daughter.

“I wholeheartedly believe that Karlie is alive,” says Zac.

Why does Karlie’s mother, Lindsay, say she believes her ex-husband and his wife know more about their daughter’s disappearance than they’re telling?

Watch the video above for a recap of Monday’s episode, then tune in on Tuesday for the conclusion of this two-part Dr. Phil.

Karlie Gusé is 5-feet-7 inches tall, 110 pounds, with brown hair and blue eyes. If you have any information about the disappearance of Karlie, please call the Mono County Sheriff at 760-932-7549. Choose option #7.

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Mom Of Karlie Gusé Claims The Missing Teen’s Dad And Stepmother ‘Refused To Call For Help When She Asked Them To’