When eleven-month-old Chad Shelton was admitted to the hospital, his liver function was abnormal, his platelet count was dangerously low, and there was unexplained bleeding from his gums, nose and eyelids. Eventually, Chad went into a coma, and died. When other people in the house began to get ill as well, investigators and scientists must frantically search for a cause.

In 1996 a woman named Stephanie Brown was driving some friends home to a foreign part of town. She took a wrong turn on Interstate 5 to get home and was later found dead in a flooded irrigation ditch.

A mapmaker surveying a boy scout ranch glimpsed something that caught his attention. At first he thought it was a turtle shell, but it proved to be a human skull. Investigators had to find a way to put a face on the victim, with only partial remains to work from. But if they could find out who she was, they might be able to determine what had happened to her.

Between 1986 and 1989, a disease swept through British cattle herds. The disease came to be known as the Mad-cow disease. Scientist began to suspect that this was somehow related to some human illness.

A serial bomber was on the loose, and he appeared to be waging a vendetta against the legal profession: A judge, two attorneys and even a courthouse had been targeted. The bombs were sophisticated and deadly, and investigators hoped they contained enough evidence to lead them to the person who built them.

Robert Sims returned home after working the night shift, and found his wife, Paula, unconscious on the kitchen floor. Their two year old son, Randy, was asleep in an upstairs bedroom, but their six week old daughter, Heather, was missing. Paula Sims was the only witness to a crime that baffles investigators to this very day.

Stephen Scher and Martin Dillon went skeet shooting in rural Pennsylvania on a beautiful Spring day in 1976. Martin was shot dead that day, and Scher maintained a freak accident had cost his friend his life. It would take more than 20 years for the truth to be revealed, and for the jury to rule on who was responsible for the death of Martin Dillon.

When four month old Ryan Stallings died under suspicious circumstances, his mother was arrested, charged, and ultimately convicted of his murder. But months later the verdict would be questioned when new evidence emerged from a startling source - his newborn brother.

Early one fall morning, Laura Houghteling left her Bethesda, Maryland home and walked to the train station on her way to work. She was never seen again. A peculiar strand of hair found in Laura's hairbrush enabled investigators to unravel the mystery of her disappearance.

In 1984, a couple set off for a camping trip but got lost and fell asleep at a scenic overlook in rural Virginia. They awoke to a person tapping on their car window; they both got out of the car to find out this man had a gun.

On September 17, 1984, in a suburb of Tucson, Arizona, eight-year-old Vicki Hoskins left home on her pink bicycle to mail a letter for her mother. She never returned, but her slightly damaged bicycle was found nearby. Investigators turned to forensic science, in the hope it would tell them not only what happened to Vicki, but also who was responsible.

When a two-year-old boy was rushed to the hospital suffering from brain seizures and breathing difficulties, doctors could not find the cause of his illness. Then the boy's sister provided an important clue, and raised the possibility of a syndrome of which few had ever heard, a syndrome that would need both medical investigators, and legal authorities.

On a cold December night in 1993, Rose Larner stopped in a convenience store on her way to her boyfriend's house. She was never seen or heard from again. Rose's disappearance remained a mystery, until a tiny clue found years later revealed a tragic tale of drugs, romance and revenge.