Only hours into the Heidt murder investigation - as Linda Heidt fought for her life - the whispers began: Rumors that this seemingly perfect Southern family was anything but.
"It's not something that I'm proud of, but it's a mistake that anyone could make..." said Robin Heidt.
Robin Heidt's "mistake" was having an affair. That happens...but an affair with your husband's brother?
Robin admits she made the first move on her brother-in-law, Craig.
"I told him that I had feelings for him that were more than, you know, brother- and sister-in-law feelings and he said that he shared the same feelings," she told Spencer. "...it just took off from there..."
Craig Heidt, the self-described "black sheep" of the family, was divorced, owed child support, was unemployed and lived off disability checks. Robin found him irresistible.
Asked if she was head over heels in love, Robin told Susan Spencer, "I was infatuated, not love."
Robin says she still loved her husband.
"Where did you think this was gonna go?" Spencer asked.
"I wasn't really sure. I was really confused... and I told Carey about it two weeks into the affair," Robin replied.
"Was he prepared for this?"
"No, he wasn't prepared and Craig did not want me to tell Carey."
"Why did you?"
"I just couldn't hide it from him," Robin said. "He knew that something was wrong with me and that I wasn't acting like myself."
But telling her husband about the affair didn't stop Robin from pursuing it. Never mind that brother-in-law thing and never mind her three children who at that time were 10, 7 and 3 years old.
"I definitely wasn't thinking about my children when I did it, how it would affect them," said Robin.
The relationship got more intense, with Robin and Craig often sneaking off to an isolated hunting cabin.
"Whenever people hear about these situations, they say, 'This is why there's divorce,' you know?" Spencer commented to Robin. "People just -- sometimes these things happen and people get divorced."
"It was very complicated, because Carey was very dead set against a divorce," Robin said. "...he told me when we were married that we were gonna be married for life."
Video: Hear more from Robin Heidt
Her husband was distraught, but he was no fool. A few weeks before he died, Carey Heidt changed his $3.5 million life insurance policy, removing Robin as the beneficiary.
"I did not find out until after Carey passed away that he had the life insurance money put into a trust fund for our three children," she said.
And his father, Philip, told Craig flat out: Knock it off with your brother's wife or lose your entire inheritance.
"There was a lot of tension... very heated conversations, several very heated conversations," Robin told Spencer. "It was very much a mess."
"I mean, this sounds like it's just completely spiraling out of control," said Spencer.
"It was, 'cause I had never seen Mr. Philip that angry," she said.
In August 2008, the weekend before the murders, Robin, once again, was up at Craig's cabin.
"So I had a few drinks there and ended up staying that night," she explained.
Robin and Craig got a rude awakening the next morning.
"We heard a helicopter that sounded like it was very low," she said,
Philip had tracked them down, enlisting a friend with a helicopter to take photos to get hard evidence of Robin's infidelity.
"I looked at Craig and I said, 'That helicopter is here watching us,'" Robin told Spencer.
"And what was Craig's reaction to this?"
"Very angry...and that Carey and Philip had better watch out or he was going to play 'old school' on them," replied Robin. "I wasn't sure; I wasn't sure what that meant."
She then went home, where she and husband Carey had a nasty argument.
"And how did this end?" asked Spencer.
"Him leaving and he said, 'I'm gonna go stay with mom and dad tonight,'" said Robin.
Asked if he had ever done that before, Robin said, "No."
"Everyone was very upset, very on pins and needles, not knowin' what to say or what to do or how they could help," Linda Heidt told Spencer.
"How did you expect this was going to be resolved?"
"I thought that Carey and Robin would probably divorce and then, if the situation between Craig and Robin still worked out, that they would be together," she said.
Later that Sunday, Robin called her lover, Craig.
"I told him that Carey had left and he asked me where he had gone and I said that he'd gone to, uh, his parents and he said, 'OK,'" said Robin.
It was the night of the murders.
"When did you find out what had happened?" Spencer asked Robin.
"Around 5 o'clock in the morning, on Monday morning," she said. "I was asleep and, um, I heard knocking on the door."
Detectives gave Robin the news.
"And the detective asked me if I knew of anyone that would have wanted to hurt Carey and Philip and I just said, '...I mean I just can't think of anything right now,'" Robin said. "I just, I was just in shock..."
"Craig doesn't just instantly occur to you?" Spencer asked.
"No," replied Robin.
"As many fights as they'd had and as much bad blood as there was at this point?"
"It did not," she replied. "It did not come in my mind right away."
She confronted her lover that afternoon.
Robin told Spencer, "I walked right up to him and I said, 'Did you do this?' and he said, 'I can't believe you would ask me that.' I said, 'I need a yes or no. Did you do this?' And he said, 'No.'"
"And you believed him?"
"I did 'cause the Craig Heidt that I know couldn't commit such an act," she replied.
Investigators weren't so sure. As Linda Heidt slowly recovered, they all wondered the same thing: Could the only surviving witness of the crime identify the killer?
