Produced by Sarah Huisenga and Dena Goldstein
This show originally aired on April 30, 2011. It was updated on Sept. 10.
COLUMBUS, Wis. - Growing up in Columbus, Wis., 31-year-old Christopher McIntyre thought he had an idyllic, small-town childhood.
"For the most part, I was a happy and normal kid growing up just like everybody else," he tells "48 Hours Mystery" correspondent Erin Moriarty.
Until the day he learned an awful truth.
"I guess I was about 9 or 10. That's when my father decided to let me know. The woman I thought was my mother I found out was not my real mother," he says. He told me...'You'll never meet your real mom. She's - she's gone.'"
Christopher was only 3 months old and asleep in his crib when his mother, Marilyn, was murdered in 1980. His father, Lane, had struggled for years to find the right time to tell him.
"I was waiting for him to get a little older," Lane tells Moriarty.
For Christopher, the truth was "confusing" and "tough" to hear.
"She never got to hear Christopher call her 'Mom,'" Carolyn Rahn says. "So much...was taken away from her."
Carolyn is Marilyn McIntyre's identical twin. Her world was torn apart when her sister was brutally murdered nearly three decades ago.
"It was hell. ...I turned to alcohol. My marriage failed," she says. "I wasn't there for my children."
"I think she feels like when Marilyn died, a big part of her died," says Carolyn's daughter, Terra Doucette, who was born less than a year after Marilyn's death.
"My first memories are seeing my mom crying on the phone about Marilyn," she says.
As Terra grew up, she witnessed her mother's constant efforts to convince the Columbus Police Department to re-open Marilyn's case.
"I couldn't tell you how many detectives we went through," Carolyn says. "We didn't know where else to turn or where to go."
In 2007, 27 years after Marilyn's murder, Terra decided to take matters into her own hands. She made a phone call that would prove to be fateful.
Ironically, she called the wrong number.
"I thought I was calling the Columbus Police Department. And instead, it was the number to the Columbia County Sheriff's Department," she says.
"I had never heard that there was an unsolved homicide within the county. It wasn't in our record system, says Detective Lieutenant Wayne Smith.
After reviewing the case, Det. Lt. Smith made a crucial decision: the Sheriff's Office would reopen the investigation.
"You could tell right away that...they cared," Carolyn says. "And they seemed shocked that it had went on this long."
As Smith and county detectives began digging into the old case files from 1980, their first question was simple: Who was Marilyn McIntyre?
"She was my best friend," says Carolyn.
Marilyn and Carolyn were born on Nov. 14, 1961. Only five years later, tragedy struck.
"Our real mother was killed in a car accident in 1966," says Carolyn.
The twins, along with older siblings Brenda and Dean, were soon living with their father and an abusive stepmother.
"It was - physically abusive, mentally, verbally abusive," Carolyn says. "And it was mainly on Marilyn and I. ... And at the age of 13, we finally moved into foster care."
At age 16, Marilyn was looking for stability in her life... something she found in 21-year-old Lane McIntyre.
"I was just enamored with Marilyn right away," he tells Moriarty. "She was so pretty. I was like, 'just control yourself.'"
According to Carolyn, "It was love at first sight."
"I wanted to take care of her, you know, be there for her," says Lane.
But while Carolyn approved of the relationship, Marilyn's older sister, Brenda Daniels, was wary.
"I just didn't think he was good enough for Marilyn," she says. "She had a rough life growing up. Was this guy gonna make it any easier? No."
Despite Brenda's concerns, the couple married on Jan. 19, 1979, when Marilyn was just 17 years old.
"It was a small party, maybe only a dozen people," Lane recalls. "But it was one of the happiest days of my life."
Soon, Lane and Marilyn added a new member to the family. Christopher was born in December of that year.
"That coming summer was gonna be the best summer of our lives, being husband and wife with our brand-new baby," says Lane.
The evening of March 10, 1980, started like any other night in the home of Lane and Marilyn McIntyre.
"We did laundry," Lane says. "And then I left for work."
"Do you remember the last thing you said to Marilyn or what she said to you?" Moriarty asks Lane.
"She said, 'I love you. Do you love me?' And, [I said] 'Of course I do,'" he replies.
The next time Lane saw his wife, she was dead.
Lee Erdmann was the Columbus police chief in 1980. He found it significant that there was no sign of forced entry or a robbery, indicating that Marilyn knew her killer.
"And what did you see when you walked in?" Moriarty asks.
"A body on the floor with a knife sticking in the side of her chest. And a mutilated head," he says. "Speculation was she might have answered the door and let someone in."
Betty Klentz, who lived in the apartment above the McIntyres, learned about Marilyn's death from Lane himself.
"It was about 5, 10 after 7:00, somebody pounded on the - our door downstairs," she recalls. "It was Lane. And he said, 'Did you hear anything last night? I just found my wife murdered.'"
By the time Chief Erdmann knocked on her door, Betty remembered that she did hear something unusual in the middle of the night.
"About quarter after 3:00 in the morning, I woke up, and the dog was just barking up a storm," she says of Lane and Marilyn's dog, Clyde. "And it was like he was pulling on something."
Asked if that was unusual, Betty says, "Well, I never heard him bark before like that."
Based on Betty's statement, police believed the murder occurred around 3:15 a.m., a time when Marilyn's husband said he was at work.
"I never left," says Lane.
Lane did, however, give police their first big lead.
"When they asked you who might be a suspect, you gave the name Curt Forbes," Moriarty tells Lane.
"I did? I don't remember," he sighs. "I probably did."
"Did you consider Curt Forbes one of your best friends?"
"At that time, yes," Lane replies. "At that time, I didn't know what he was capable of."