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Merrilee Cox-Lafferty, a 37-year-old California mother, disappeared in August 2018 while on vacation in Utah. She took her minor daughter and her service animal, Coco, along. Her trip consisted of visiting a long-standing acquaintance, Stacy Robert Willis. The investigators used digital data, footage, and witness statements after her disappearance to follow her last movements.
Her dog was subsequently located walking alone, which was a turning point in the investigation. Authorities finally found Merrilee's body in a secluded area of Blacksmith Fork Canyon. Willis was arrested and indicted for killing her.
The Merrilee Cox-Lafferty case was featured in the episode titled The Dog Knows on Investigation Discovery’s series See No Evil. This episode aired on Tuesday, June 24, 2025, at 9 p.m. ET on the Investigation Discovery (ID) channel. It was also made available for streaming the same night on Max and Discovery+ platforms.
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Fact-based timeline of Merrilee Cox-Lafferty's murder
August 17, 2018
- Merrilee Cox-Lafferty departs California and heads to Cache County, Utah, with her child and her service dog, Coco.
- As per reports, Merrilee suffered from epilepsy and had Coco to help her.
August 18, 2018
- Merrilee is seen alive for the last time in Logan, Utah.
- As per KSL, she visits Stacy Robert Willis, an old friend, to drop off two bags of marijuana and receive cash.
- Merrilee's daughter eventually informs the police about the sale of drugs and that she noticed her mom fighting with Willis.
- Willis reports to police that they fought in the parking lot of his apartment complex and that he blocked Merrilee's number subsequently.
- Witnesses confirm Merrilee was at Willis' home. Surveillance is recorded showing Willis arriving at work with Coco, but not Merrilee.
- Later that day, phone records indicate Merrilee's cellphone pinging close to Blacksmith Fork Canyon at 1:30 p.m., and again close to Logan 45 minutes later.
August 19, 2018
- Willis takes Merrilee's daughter to Mountain Home, Idaho, and drops her off with a friend.
- Deseret News reports that Merrilee's vehicle is later discovered abandoned in Boise, Idaho, some 300 miles away.
August 21, 2018
- Merrilee Cox-Lafferty's family declares her officially missing.
- Her service dog, Coco, is spotted roaming around a street in Logan which is red-flagged and heightens police suspicion.
- The Cache County Sheriff's Office sends out a missing person alert.
Late August – early September 2018
- Police investigators start analyzing surveillance videos and cell phone records.
- Reports state that a friend of Willis informed police that Willis confessed to murdering Merrilee Cox-Lafferty when she accidentally hit his SUV with her car into a tree. He explained that he had assaulted her and then buried her remains at a secluded camp.
- The site they refer to is Left Hand Fork, an isolated part of Blacksmith Fork Canyon.
September 14, 2018
- Merrilee Cox-Lafferty's body is discovered in a shallow grave eight miles down Left Hand Fork Canyon.
- Police arrested Stacy Robert Willis of Hyrum, Utah, on allegations of aggravated murder and several other crimes.
- The burial place was off the beaten path and hard to find, Deseret News reports.
September 15, 2018
- Law enforcement verified that the discovery of Coco helped crack the case.
- Logan Police Chief Gary Jensen indicates the service dog "turned this case in the right direction" (Deseret News).
Post-arrest legal proceedings
Willis is held without bail in Cache County Jail. He is accused of capital murder, obstruction of justice, unlawful possession of a firearm, drug offenses, and criminal mischief. Prosecutors indicate that the motive was a mix of drug-related disagreement and personal altercation. A preliminary hearing occurred on October 1, 2018.
The case of Merrilee Cox-Lafferty received fresh media attention in June 2025 via Investigation Discovery's See No Evil: The Dog Knows, which recreates the timeline and the digital forensics.
