Nichol Kessinger had no idea that the man she was in a relationship with was about to become a cold-blooded killer.
Initially he denied knowing anything about their whereabouts, but eventually he confessed to murdering Shanann Watts, and her daughters Bella, four and Celeste, three.
Watts was having an affair with Nichol – who he had told he was going through a divorce when they first met.
They had met when Nichol was working as a field engineer for Tasman Geosciences in 2018.
Watts and Nichol quickly became friends, and two months before he murdered his family, their relationship became romantic.
At the same time, Watts was still playing happy family, with his wife expecting their third child – who they planned to call Nico.
But on August 12, 2018, Watts strangled Shanann to death after a fight about the affair.
He then went on to drive to an oil site with the body in the back, and smothered his two girls, before disposing of the dead bodies.
When Nichol found out what Watts had done, she was horrified and did all she could to help the police.
She went on to tell officers all about the lies he had told her.
Nichol actually had key information that Weld County District Attorney Michael Rourke described as being “a bombshell”.
Devastatingly, her brave actions means she had had to go into witness protection, assume a new identity, and move away from everything she knew.
Nicole explained: “It's not fair. It wasn't fair to me in the first place, it wasn't fair to her in the first place, it wasn't fair to any of us in the first place.
It wasn't fair to his family for him to have an affair, it wasn't fair to me to have him lie to me and make me think that everything is going to plan. And still to this day, I don't even know what's a lie and what's not."
"It's like, you know, I'm gonna wake up every day and know that like this mom and her unborn child and these two little girls are not around anymore and it breaks my heart."
Watts was pleaded guilty to five counts of first-degree murder, including an additional count per child because they were under 12.
He also pleaded guilty to three counts of tampering with a dead body, and an unlawful termination of a pregnancy.
Watts is currently behind bars in Wisconsin, US, after being sentenced to five life sentences with no chance of parole.
American Murder: The Family Next Door is streaming on Netflix now.