The crime scene was awash with blood, bespeaking the horror of the crime: the murder of two young boys and the stabbing of their mother. Forensic scientists carefully analyzed the blood evidence and found it told the story of an assailant who had gone to great lengths to alter the crime scene.

Scott Dunn was missing and, at first glance, nothing seemed out of place in his apartment. Then police found faint blood spatters on the ceiling and walls, and a bloody carpet pad underneath a new piece of carpeting. When they sprayed the bedroom with luminol, a scene of horrific violence emerged. Now investigators faced a daunting task: to prove Scott Dunn had been murdered, even though they had no body, no weapon, and no witnesses.

On a windy Kansas night in October, 1995, a mysterious fire swept through the home of a prominent doctor. Two of her family members made it out alive; two did not. In the debris, investigators found evidence which told them much more than how the fire started.

In 1990, Shirley Andronowich's body was found one morning after she was murdered and mutilated. Eyewitnesses told police Shirley and her husband Ed were seen fighting in a bar the night before. Police first suspected Ed and even arrested him after he confessed to the murder. But all forensic evidence proved that Ed had actually nothing to do with the crime. Originally aired as Season 4, Episode 4.

Sometime during a neighborhood Christmas party, five-year-old Melissa Brannen disappeared. No one saw where she went or noticed anything unusual. Investigators turned to forensic science to help them see what the witnesses missed. The young girl was never seen again... but fiber analysis led police to a suspect nonetheless.

The doctors at the hospital couldn't determine the cause of Bobby Curley's hallucinations and intense pain. At first, they treated it as a neurological disorder, Guillen-Barre Syndrome. But Bobby's condition deteriorated. Something he was being given in the hospital wasn't curing him, it was poisoning him.

Who was the sexual offender that murdered two adolescent boys in Nebraska? A criminal profiler from the FBI said he would definitely kill again. The key to stopping him would be the unique composition of the "junk rope" he used to tie his victims. Omaha police and the FBI use rope analysis, psychological profiling, forensic odontology, and even hypnosis to bring a 116-day manhunt to a close, and solve yet another murder in another state.

Karla Brown was found brutally murdered in the basement of her home. There was little evidence at the scene, and it began to look like the killer had committed the perfect crime. Then investigators noticed something in the crime scene photographs that had previously been overlooked: The killer had left behind an important clue after all.

Janice Johnson was found dead at the foot of her basement stairs. Police in Nova Scotia had to unravel the circumstances surrounding Janice's death and answer the question: Was it an accident... or murder? Different authorities rule both ways, and it takes years - and a astonishingly unique recreation of the death - before justice is finally done.

In 1996, more than a dozen children in Seattle, Washington, were fighting for their lives. Each one of them had contracted a serious illness, and no one knew what it was. When one of the children died, investigators knew the clock was ticking... and they needed to isolate the cause and find the cure before time ran out. Epidemiologists and other scientists find all the victims contracted the same strain of bacteria... but how?

On a September night in 1966, Dianne Keidel met a friend for a drink, and afterward, she disappeared. Investigators were unable to determine if Dianne was the victim of foul play, or if she couldn't face the responsibilities of being a single mother with four young children. That question was answered twenty-seven years later, when her daughter came forward with a fantastic tale of something she remembered seeing when she was only five-years-old. Could ground-penetrating radar and forensic anthropology help solve the mystery that haunted a young child all the way into...

Young Navajos on a reservation in the southwest were dying at an alarming rate. CDC officials had never seen anything like it; the mysterious illness had claimed the lives of more than 20 people. The tribe's medicine men provided investigators with a critical clue... which would lead halfway around the world to a most unlikely killer.

While on a business trip in 1986, Ed Post started his day by jogging in downtown St. Louis. When he returned, he found his wife lying face-down in the bathtub, unconscious. She was rushed to the hospital, but it was too late. She had drowned. Was it possible a faulty towel ring was to blame? An industrial testing laboratory, an accident re constructionist, metallurgy analysis and a determined detective unravel a family's secrets and the truth about what happened in the hotel bath.

A trio of unsolved murders that occurred in Wichita Falls, Texas during the 1980s, details how a fourth murder from the same time period provided the police with more than they realized. John Little, an investigator for the DA's office, picked up the cold cases years later. He soon connected the fourth crime's confessed killer to the other murders. Originally aired as Season 8, Episode 40.