Nichol started dating a co-worker who seemed like the ideal partner. His name was Chris Watts.

When Nichol Kessinger met Chris Watts at work in June 2018, she thought she had stumbled across something rare: a man who listened, who seemed gentle, who claimed he was starting over.

Chris told her he was separated, finalising a divorce, and quietly moving on with his life. He never wore a wedding ring. To Nichol, it appeared he was a man trying to do right by his children while leaving a broken marriage behind.

They began seeing each other in July. Their relationship quickly became intense — spending four or five nights a week together. Nichol wanted to take things slowly, it was still early days, but he seemed safe and trustworthy.

"We had just met," Kessinger said. "I barely knew him."

But Chris Watts was not who he claimed to be.

Chris Watts and wife and daughters. Image: Supplied.

"He lied about everything."

In reality, Chris's wife Shanann was still very much in the picture — and she was 15 weeks pregnant with their third child. Nichol had no idea.

On August 13, 2018, the truth started to surface.

Watts had been texting Nichol all day, saying he's been busy and chatting like normal. But at around 3:45pm he sent her a text saying his family was 'gone'.

The Denver Post reports that he told Kessinger that Shanann had taken the girls to a play date and not come home.

His texts were emotionless, casual. She was confused when reporters began to show up at Watts' home.

Then the truth hit.

Nichol learned that he was still married — and contrary to leaving his wife, she was actually 15 weeks pregnant. She sent him a flurry of messages asking for answers.

"I kept asking him, 'What did you do, Chris? Where's your family?'" Nichol would later say. "He made me believe he was divorced. He lied about everything."

Alarmed, Nichol went to police. She told them everything — the affair, the lies, her fears. For investigators, she quickly became a crucial witness.

"I just wanted to help," she told the Denver Post. "With a pregnant woman and two children missing, I was going to do anything that I could."

The murders.

Soon, the devastating truth was revealed. On August 15, Watts was arrested.

From the outside, the Wattses were a happy family. But there was a sinister underbelly.

A family friend told People in August 2018 the couple had been having "marital problems" and had previously struggled with their finances.

Meanwhile, a contractor who worked for Watts said he watched the father-of-two change over the summer of 2018.

"I watched him get more and more unhappy with his life," he told People.

"He went from being a friendly guy to being withdrawn and angry. I saw him lose his temper over little workplace annoyances. He had an irritable side with the contractors. He could be combative."

It all came to a head in the early hours of August 13, when Chris had strangled Shanann in their Colorado home, after admitting to his affair.

He then smothered his daughters Bella, four, and Celeste, three, before disposing of all three bodies at a worksite owned by his employer. Shanann and her unborn son were buried in a shallow grave, while his daughters were placed in vats of crude oil.

At first, Chris tried to blame Shanann, telling police she had killed the girls before he killed her in a rage. But his story quickly collapsed. He pleaded guilty to nine charges, including murder, and was sentenced to life without parole.

The aftermath.

Image: Getty.

Nichol was never suspected of involvement in the murders. But her life was irrevocably changed.

Overnight, she went from private citizen to "the mistress" of one of the most infamous family annihilators in recent history.

Chris, meanwhile, tried to shift blame onto her. In prison letters, he referred to Nichol only as "Jezebel" — a biblical figure associated with seduction and betrayal — claiming she was the reason he lost his family.

The courts disagreed.

Evidence showed Chris alone planned and carried out the murders. Nichol's only role was that of a woman who fell for a man living a double life, a man she thought was divorced, a man who convinced her he was someone he wasn't.

A chilling legacy.

Years on, Nichol's story remains one of deception and shock.

She thought she had found someone to spend her life with. Instead, she had unknowingly become entangled with a man who would murder his entire family.

For Shanann's family, the grief remains overwhelming.

For Nichol, so does the knowledge that the man she trusted turned out to be a monster hiding in plain sight.

Featured image: Facebook.