Dr. David Cornbleet, a beloved Chicago physician, is stabbed to death in his office one October evening in 2006. His son, Jon Cornbleet, can’t imagine why anyone would want to kill his father. While some physical evidence was left at the crime scene, the cops are most interested in the office building’s surveillance tape, which captured the figure of a young man whom they believe is the primary suspect. Neither Jon nor the Chicago police have any clue as to who this person is or how to find him. Jon vows at his father's grave site to do everything he can to find the murderer, but he knows his search will have to be unconventional. What will be his strategy? Jon decides to use a social-networking site to cast his net as wide as possible. He believes that someone, somewhere on the Internet, will have answers for him.

At 6 a.m. on Feb. 1, 1988, in a wealthy suburb of Durham, N.C., 39-year-old Russell Stager is shot in the back of the head while asleep in his home. His wife, Barbara, is mumbling incoherently on the edge of the bed when the police and EMTs arrive. Barbara tells police she thought she heard an intruder. Frightened, she'd reached for the gun her husband kept under his pillow, and somehow, it fired. The police write up the report as an accidental shooting, but when Russell's high-school sweetheart and first wife, Jo Lynn Snow, learns of the shooting, she suspects foul play. Jo Lynn tells the investigating detective that Barbara Stager's first husband died the same way, from an "accidental" gunshot wound. But is a "hunch" by a friendly first wife enough to change the course of the police investigation? What will Jo Lynn have to do to prove her suspicions? And will the death of Russell Stager be considered more than a tragic accident?

In January 1990, Mike and Penny Moreau learn that their 21-year-old son, Tim, a college student living in Portland, Ore., has vanished without a trace. The only lead comes from Tim's boss, Larry Hurwitz, the owner of a popular nightclub in Portland. Hurwitz tells police and the Moreaus that he caught Tim selling counterfeit tickets, and Tim ran out of town, to avoid facing charges. Mike and Penny are convinced that if their son had been in trouble, he would have called. Months go by, and the police investigation hits a dead end. The Moreaus make a promise to each other -- they will not rest until they find out what happened to their beloved son. Over the years, the Moreaus fly to Portland more than a dozen times, chasing every tip that might lead them to Tim, whether he's dead or alive. But Tim is never found, and the Moreaus struggle with how to move on without their eldest child. Then, years later, with the help of a local Portland reporter, Mike and Penny discover the most promising information yet -- which leads to a case of income tax evasion. But what does a case of income tax evasion have to do with Tim Moreau? Will Mike and Penny ever learn the truth about their son's mysterious disappearance?

In April 1982, Bernie Sheppard, of Olympia Fields, Ill., learns that his 23-year old daughter, Deborah, has been found dead in her apartment in Carbondale, Ill. Deborah, a senior in college who is days away from graduating, is suspected of a drug overdose. Her father Bernie doesn't buy it, insisting that his daughter didn't do drugs. Bernie flies his daughter's body to a famed forensic pathologist in Chicago, for a second autopsy. The results devastate Bernie and his wife Hazel: Deborah had been sexually assaulted and then strangled to death. As the police begin tracking down possible suspects, her father starts his own investigation. Bernie travels to Carbondale numerous times, questioning Deborah's friends and classmates, and following every lead that comes up, but he finds nothing that gives him the answer he so desperately seeks. The police pursue their own investigation, but soon enough, the case reaches a dead end. Decades pass and Bernie's hunt for the killer is never far from his mind. Will his daughter's murder ever be solved? Will the killer be brought to justice?

The case of Clarence Elkins, who was wrongfully convicted in the 1998 murder of his mother-in-law. He was exonerated by DNA evidence in December, 2005.

The 1988 murder of 32-year-old Debi Whitlock in her Modesto, Cal., home is discussed.

Sherrie Gladden-Davis recounts the 1991 disappearance of her sister, Fran Gladden-Smith. Also: The 1995 shooting of 16-year-old Mikey Valadez at a busy San Antonio intersection is discussed

Examining the case of Roy Brown, who was convicted of a 1991 murder he didn't commit. He spent 15 years in prison before he was exonerated by DNA evidence in 2007. Also: A journalist searches for the men who killed his father 29 years earlier.