"I would've done anything for her," Wallace said. "But she tried to kill me instead."
In 2000, Castor's first husband, the man she called "the love of her life," seemingly passed away from a heart attack. Wallace left Stacey Castor behind with their two daughters, Ashley and Bree Wallace, who is now 18.
The bizarre death of Castor's second husband within five years of the death of her first husband made investigators suspicious.
David Castor's death initially was thought to be a suicide by antifreeze poisoning. Stacey Castor buried him in a grave plot right next to her first husband.
Shortly afterward, investigators exhumed Michael Wallace's body and discovered traces of ethylene glycol, a chemical found in antifreeze.
What's more, forensic lab workers said the exact same chemical was found in David Castor's body.
Police concluded that Wallace also had died from antifreeze poisoning -- and that both men had been murdered.
Wallace's eldest daughter, Ashley Wallace, was distraught.
"I started crying. I got upset," she recalled. "Why would they dig up daddy? Like, he was resting peacefully. I thought it was inhumane, and I didn't like it whatsoever."
Soon, Stacey Castor became the main suspect. Police wiretapped her telephone calls, and in a conversation with close friend Dani Colman detectives heard Stacey Castor's worry and her denial of accusations.
"It scares the living [expletive] out of me because I didn't do this," Stacey Castor said in one of her phone conversations.
Her longtime friend is one of the few people that maintain Castor's innocence.
Colman told ABC News, "Stacey is my best friend. The person that I know wouldn't do this."
Castor's mother, Judie Eaton, also is her staunch supporter.
"I have woke up in the middle of the night and you just lay there and you think, 'How did this happen?'" said Eaton.
Eaton believes her daughter is innocent, and furthermore, she is convinced that her own granddaughter, Ashley Wallace, is responsible for the murders of David Castor and Michael Wallace.
Bree Wallace laments her family's division.
"I feel like [Judie Eaton] took sides and she didn't have to," Bree Wallace said. "She still could have supported my mother and everything. But she didn't have to accuse my sister."
When the verdict was delivered Feb. 4, 2009, Stacey Castor was in disbelief. She was found guilty of second-degree murder and second-degree attempted murder.
"I think honestly that was the best day of my life," Ashley Wallace said. "Because I knew that people knew, I knew that they knew that I didn't do it."
Stacey Castor told ABC News she recalled thinking, "It can't be happening. It's got to be wrong."
She added that she believes she did not receive a fair trial.
"We weren't allowed to present a defense. There were things that were allowed in that shouldn't have been, things that should have been that weren't," she said.
After being asked repeatedly, Stacey Castor did not say what evidence or which witnesses would have altered the result of the trial.
Despite her denials, a judge sentenced Stacey Castor to more than 50 years in prison, the maximum sentence.