Hallie Pritchard set up a laptop recording device in her room in hopes of catching her sisters stealing her clothes.
"I hit record and just put all the pillows around [the laptop]," said Pritchard.
The 12-year-old was eager to check the surveillance videe, expecting a to catch her sisters red-handed. Instead, she was shocked to find herself watching "To Catch a Thief."
"He walked up to my desk, opened the drawers, looked in, and he put his hand in and was picking things up and put it in his pocket," said Pritchard.
The video shows a man all alone in her room, rifling through her drawers. A total stranger, totally unaware he was being filmed.
"Instead of catching my sister, I caught a man stealing stuff out of my desk," said Pritchard.
It happened while Pritchard's parents were holding an open house in hopes of selling their home in Orinda, California, just outside San Francisco. Any potential buyer could wander around.
"My mom's missing a diamond necklace and diamond bracelet," said Pritchard.
The alleged thief's name is Douglas John Callandra, and cops say he's done this before. He's a former real estate agent who was convicted in 2010 for stealing more than 50 items from people's homes and selling them on ebay.
Pritchard's parents, Chris and Jody, could barely believe it.
Chris told INSIDE EDITION, "She came running down the stairs and was screaming that we had been burglarized."
Jody said, "I was in disbelief. I didn't believe her that she caught someone on tape. I thought she was kidding."
With the webcam evidence, Callandra was arrested and is being held without bail because he's still on probation for the earlier conviction.
So a sticky-fingered man is caught in a web of his own deceit, thanks to a young girl with a webcam.