When Sarah Maguire, aged 29, was found savagely murdered in Tulsa, Oklahoma in January 2022, it was soon suspected that her killers may have been attempting to remove her from an alleged “love triangle.”

Maguire’s life came to a tragic end after she was beaten with a crowbar and left to die on her couch. Nicholas Johnson and Brinlee Denison, individuals she trusted, remained in her home just long enough to carry out their heinous act.

The brutality and callousness of Maguire’s murder left the community in shock. “The sick, twisted details of the two of them having sex in the victim’s bed, admitting to being able to hear the victim struggling to live…” remarked local KOTV reporter Reagan Ledbetter to Snapped: Killer Couples, which airs Sundays at 6/5c on Oxygen. “If that doesn’t give you chills and make you mad and angry, I don’t know what does.”

What happened to Sarah Maguire?

After growing up on an Oklahoma farm, Sarah Maguire moved to Tulsa and found a successful early career as the office manager for a towing company. “Sarah was the central hub of that workplace,” remembered Jamie Stavinoha, her younger sister. “Sarah had such an all-encompassing love and protective nature for people, family, friends.”

But through her recent relationship with a local man (whom police would quickly rule out as a murder suspect), Sarah was introduced to Brinlee Denison, a mutual acquaintance who needed a place to stay. Sarah freely offered Brinlee a spot in her backyard shed, and it was through that connection that she also met Nicholas Johnson — a married man with children who, on the side, had kept up an “on-again, off-again relationship” with Brinlee, according to Tulsa County prosecutor Allison Connor, as seen on Snapped: Killer Couples.

Under police questioning, both Denison and Johnson told investigators that Brinlee had developed a rapid romantic interest in Sarah. But, said Connor, “where her relationship with Sarah began versus where that relationship with Nicholas ended is a bit murky.”

What wasn’t murky was the decisive brutality of Sarah’s murder. Responding to a welfare request after she didn’t show up at work, Tulsa police went to Sarah’s home, saw a figure on her couch through a window, and upon entering discovered her dead body, badly beaten and covered by a blanket.

“When they remove that blanket, they see this woman with gash marks and blood all over her face… blood matted in her hair,” Connor told Snapped: Killer Couples. “The injuries were quite severe.”

How were Nicholas Johnson and Brinlee Denison caught?

In a room in Sarah’s house, investigators found the presumed murder weapon: A crowbar, cleaned of blood and conspicuously placed on a dresser. They also found that Sarah’s car was missing, prompting police to issue an alert to be on lookout for a vehicle bearing its description and tag number.

Sarah’s bereaved mother granted investigators access to the records from the banking card she shared with Sarah, and they immediately saw that someone had taken the card and was using it to make purchases that they could track. From Tulsa, they followed the spending spree across the state line to Fayetteville, Arkansas, where local police located not only Sarah’s vehicle at a fast food restaurant — but both Denison and Johnson along with it.

The search for suspects connected to Sarah’s murder had taken less than two days. Once Denison and Johnson were in police custody, each confessed to knowing details about her murder, but told Tulsa investigators conflicting stories about the role each claimed to play in the killing.

Denison portrayed Johnson as a jealous lover in their alleged three-way relationship; an enraged boyfriend angry that the two women appeared to be romantically involved without his participation. In her version of events after the murder, Denison claimed to be more Johnson’s captive than his willing accomplice and travel companion — but investigators found her story unconvincing.

“Brinlee says Nicholas had seen some photographs of Brinlee and Sarah; maybe some scantily clad photographs that really upset him,” said Connor. “…Brinlee claims that she and Sarah were in a relationship. But outside of Brinlee’s statements, there was really not much that we could say, ‘Yes, that’s true,’ or ‘No, that’s not.’ I do not believe that any photograph of Brinlee and Sarah was ever recovered.”

While Denison was telling police that she had been Nicholas’ frightened hostage during their brief time on the run since Sarah’s murder, Nicholas offered a very different version of events, according to Snapped: Killer Couples.

“Nicholas did the exact same thing as Brinlee — he started to point more towards Brinlee as being the problem,” said retired Tulsa police detective Tim Bracken. “She talked him into it. She’s the one that wanted to murder Sarah. She’s the one that wanted to take the car and the money and all that. She was the mastermind.”

Video surveillance footage from the fleeing couple’s stop at a Walmart store ultimately persuaded police that Brinlee Denison’s story — that she was little more that a frightened ride-along captive while Nicholas Johnson held her hostage after the murder — simply couldn’t be true.

“We see that Nick had actually gone into the Walmart by himself to do this transaction. She remained in the car. And that kind of debunked the whole ‘kidnapping,’” said Bracken.

“I believe he was in there for about 20 minutes and, at that point in time, she’s in a public place,” added Connor. ”There are a number of individuals who she could have sought help from. She was not this ‘victim’ that she tried to paint herself out to be.”

Both Denison and Johnson were charged with first degree murder for the death of Sarah Maguire. But before facing trial, Johnson pleaded guilty to the charge and was subsequently sentenced to life in prison without the possibility of parole.

After a judge later ruled that there was insufficient evidence to try Denison for first degree murder, she pleaded guilty to a lesser charge of accessory to murder, and was sentenced to 20 years in prison. Denison will be eligible for parole in 2039 at the age of 42.