[This story originally aired on Sept. 29, 2007.]
On May 5, 2004, John Runge of the Virginia Beach Police Department got a call from a fisherman stating that he had found a suitcase floating in the Chesapeake Bay.
"I opened the bag up, unzipped it, noticed that there were trash bags, black colored trash bags in the suitcase," Runge remembers. "Once I peeled the trash bags back I saw a pair of human legs from the knees down."
Five days later another suitcase washed up on the shores of Fisherman's Island; inside that suitcase was the torso of white male severed from the waist down. His head and arms were still attached. Later, a third suitcase with body parts was found by a fisherman and his wife.
The victim was eventually identified from a sketch: William McGuire, from Woodbridge, N.J.
McGuire was married to Melanie, who tells correspondent Maureen Maher, "When I heard how my husband was killed I was in complete disbelief and I could not imagine what he went through."
But Virginia homicide detective Ray Pickell had doubts. "I did not believe that Melanie McGuire was a grieving widow," he says. "I believe that she was responsible for her husband's death."
But Melanie insists she is innocent: "I did not kill the father of my children. I did not kill my husband."
Three months after the body of Bill McGuire was found in the Chesapeake Bay, his beautiful wife was not only a widow -- she was also a murder suspect.
"48 Hours" gave Melanie a video camera to document her innermost thoughts and fears. These video diaries, which she shot in the quiet of her bedroom near the Jersey Shore, captured Melanie in her most private and tortured moments.
Shown on "48 Hours" the first time, they are a rare glimpse into the mind of complex woman, who some say is a caring mother, others say a calculating killer.
"I can't help but think if I had made better decisions along the way, and left the marriage earlier, that I wouldn't be sitting here," Melanie confided in one of her video diary entries.
It is the last place anyone -- especially her mother Linda Cappararo -- ever expected to find Melanie. "She was every mother's dream. A good girl. Never got in trouble," Cappararo says. "Very supportive of her family. Happy. Wonderful student."
Melanie became a nurse. "There were several times where she would see an accident on the side of the road and she would stop the car and go over and assist. She was always there for people," Cappararo tells Maher.
It was a quality that caught the eye of then-28-year-old Bill McGuire, a veteran of the U.S. Navy.
Bill's sister, Cindy Ligosh, says Bill and Melanie were a perfect match from day one. "They were equals," Cindy remembers. "They both wanted the same things out of life or so I thought."
The couple married in June 1999. Less than a year later, the McGuires had their first son.
Melanie went to work at a fertility clinic and Bill began teaching computer science at a technical college. Melanie remembers this as a happy time for her. "I saw Bill morph into kind of a family man that he always wanted to be and it really touched me."
But, as with so many couples, the relationship did not withstand the test of time. By the birth of their second son, the couple had grown even further apart. One reason, according to Melanie, were Bill's frequent trips to Atlantic City. She says her husband had a gambling problem.
Melanie says Bill became increasingly erratic, even volatile. She remembers one night he called from the road in a rage after getting a speeding ticket. She hung up on him.
"He called back, cursing any number of obscenities at me. And told me that if I was there when he got home he was gonna kill me," Melanie tells Maher.
Melanie says she didn't believe him, but says she was scared.
Despite the ongoing battles, Melanie agreed to buy a new house with Bill. Why, if she was so unhappy, would she agree to a 15 to 30 year commitment of buying a home?
Says Melanie, "For the kids. Even though we weren't happy we weren't ending this marriage any time soon that I could see."