WHEN A 911 OPERATOR VANISHES INTO THIN AIR HER DEADLY SECRET IS EXPOSED, ON 48 HOURS MYSTERY, SATURDAY, JAN. 30

When Theresa Parker unexpectedly disappeared in March 2007, the small town of LaFayette, Georgia, was shocked. So beloved was the 911 dispatcher that hundreds of people came out to search nearly 175 square miles of land for her.

Theresa, who loved helping others, was adored by family and friends including her police officer husband, Sam Parker. The couple, who married in 1993, seemed a perfect match. But after 13 years of marriage the two decided to split and Theresa found her own place. One night after visiting her sister, Theresa left to go home, but was never heard from again.

Police found her car at the couple's home, but there was no sign of Theresa and no obvious signs of foul play. Investigators' extensive search of the heavy terrain around the home would not turn up a body, but as they turned their focus to her husband Sam, the probe would soon expose his dark side and Theresa's deadly secret.

Click here to watch a preview of Tracy Smith's report in 48 HOURS MYSTERY: "The Secret," to be broadcast on Saturday, Jan. 30 (10:00-11:00 PM, ET/PT) on the CBS Television Network. Click here for Smith's reporter's notebook.

This broadcast is produced by Marcie Spencer and Michelle Feuer is the field producer. Peter Schweitzer is the senior producer. Al Briganti is the executive editor. Susan Zirinsky is the executive producer. CBS News 48 HOURS MYSTERY broadcasts are available on iTunes.