WHEN AN AMBITIOUS COLLEGE STUDENT VANISHES, ONE PHONE CALL CHANGES EVERYTHING -- "48 HOURS MYSTERY," SATURDAY, JAN. 21

When Shannon Melendi, an ambitious 19-year-old sophomore at Emory University in Atlanta, disappeared in March 1994, authorities believed she had run away. Police even thought it might be a college prank. Nearly two weeks later, a mysterious phone call changed the course of the investigation. Correspondent Troy Roberts reports for 48 HOURS MYSTERY: "The Phone Call," to be broadcast Saturday, Jan. 21 (10:00-11:00 PM, ET/PT) on the CBS Television Network.

Melendi grew up in a high-profile Miami family. Her parents say she was born to be a leader and dreamed of becoming a Supreme Court Justice. While at college, Melendi worked as a scorekeeper at a softball park, which was the last place she was seen.

Melendi's roommate, Athena Perez, says she became worried when her friend didn't return to the dorm room the evening of March 26. The next day, Perez and her friends found Melendi's abandoned car with the keys in it and called police. Perez says the officer who came to the scene took information, but was very laid back about the incident and told her to drive Melendi's car back to campus.

Deeply concerned about her roommate, Perez called Melendi's parents, who immediately left Miami for Atlanta. The Melendi's say the police told them they thought their daughter ran away, not to worry and that she'd return. The Melendi's insisted to police that their daughter would never run away.

An extensive police search of wooded areas and waterways turned up no signs of the missing girl. That's when family and friends began their own aggressive search. They offered a $10,000 reward for information and tapped into celebrities Andy Garcia and Bo Jackson, who appeared on national television programs, including "America's Most Wanted," in an effort to help find Melendi.

Then, nearly two weeks after Melendi vanished, an anonymous male phoned the Emory University counseling center. The caller said he had Shannon. The FBI traced the call to a pay phone where police found evidence that was intentionally left behind by the caller; a package containing a ring that belonged to Melendi.

Only then did authorities treat the case as a kidnapping. Investigators managed to trace pieces of the package to a local man, Colvin "Butch" Hinton, III. It turned out Hinton was an umpire at the softball field where Melendi worked the day she went missing.

Authorities searched Hinton's house and property with dogs and heavy digging equipment, but found no human remains and nothing that could be linked to Melendi. However, they were shocked by what they did find: other women's sweaters and plastic pants often worn by police at crime scenes.

Investigators would determine that Hinton had a violent criminal past covering decades. But, with no crime scene in the Melendi case and no evidence that she was dead, proving Hinton had committed murder would pose an unprecedented challenge for prosecutors.

48 HOURS MYSTERY: "The Phone Call" is produced by Ira Sutow and Marcelena Spencer. The executive editor is Al Briganti and the executive producer is Susan Zirinsky.