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Marilyn Mock walked into a Dallas foreclosure auction to help her son buy a house. She walked out with a friend for life.

Outside the auction hall, she'd noticed a woman who was lost in thought as the auctioneer brought down the gavel. "I asked, 'Are you here to buy a house?'" says Mock, 50, a married mother of three. Pointing to item no. 73, the woman started crying: "That's my house," said 38-year-old Tracy Orr.

In 2003, while working as a mail carrier, she bought the fixer-upper for $5,000 and moved it to a one-acre lot she owned in Pottsboro, north of Dallas. Taking out an $80,000 mortgage, she put in a new roof, electricity and plumbing. "It was just an old farmhouse," says Orr, a divorced mother of a 19-year-old daughter. "But I planned on dying there." Then she lost her job. Last June, days away from eviction, she moved into a rented trailer. She'd come to the auction to say goodbye.

But when Orr's house came up, "I just started bidding," Mock says. Winning the house for roughly $30,000, she told Orr: "I did this for you." Now Mock will make monthly payments on the home while Orr lives there, re-paying Mock whatever she can and, hopefully, buying back her house one day. Why go to such lengths for a stranger? "I do this stuff," shrugs Mock, a rock-yard owner who once took in a troubled youngster. As for Orr, she's begun to emerge from despair: "One act of kindness can change your whole outlook. That's what Marilyn did for me."

Please tune in to CNN HEROES: An All-Star Tribute featuring the best of PEOPLE's 2008 Heroes Among Us, hosted by CNN's Anderson Cooper, on Thanksgiving, Thurs. Nov. 27, at 9 p.m. on CNN.

Know a hero? Send suggestions to HEROESAMONGUS@PEOPLEMAG.COM

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