The story gripped the region. In 2010, a Fallbrook family of four just up and vanished. No apparent reason to have left. No evidence of foul play.

More than three and a half years would pass until a dirt-biker stumbled across the skull of a child in the desert near Victorville, a disturbing find that led investigators to shallow graves with the remains of Joseph and Summer McStay and their preschool-aged boys. Several years later, a McStay friend and business associate who insists he is innocent would be found guilty of their slayings.

In her new book, “Down to the Bone: A missing family’s murder and the elusive quest for justice,” local author Caitlin Rother closely examines the McStay case, from pouring through files to viewing the trial to talking directly with some of those involved, including Charles “Chase” Merritt, the man convicted of killing the family.

Rother, a former investigative journalist, dug through hundreds of pages of court documents and spent days at a San Bernardino courthouse going through 1,200 pieces of evidence. She also received thousands of pages of law enforcement investigative files — a “treasure trove,” she called it.

All that research led her to uncover details not revealed during the trial — “all kinds of new and exclusive stuff that has not appeared anywhere else,” Rother said.

“I found out a lot of things, which I ended up putting in the book, about the investigation and the way it was conducted and who knew what, when, and who they talked to, and what they ignored, and what they chose to focus on,” she said.

Among new details not included at trial: Joseph McStay had owned a gun, which years later turned up in an abandoned car in Las Vegas.

She walks readers through the case, including what she says were flawed investigations and confirmation bias. She shares the paths investigators went down, who they looked at and what their work turned up, including concerning another former McStay business associate, who could not be reached for comment Monday. The only person arrested as a suspect was Merritt.

“It was amazing to me by the end of the book, when I finished it, what a total mess this case was, and that I still don’t know who killed this family,” Rother said. “You would think that with all that research and all that careful examination of the evidence that was collected, that it would be clearer. But it’s not.”

The San Diego County Sheriff’s Office, which handled the initial investigation before concluding the family had likely gone to Mexico, declined to comment on the book. The San Bernardino County Sheriff’s Office, which took over the case after the remains were found, said the now-captain who led its investigation has not read the book and could not comment.

Merritt’s former defense attorney, James McGee, said he could not comment without Merritt’s permission. His other defense attorney, Raj Maline, did not respond to a request for comment Monday.One of the prosecutors, Deputy District Attorney Britt Imes, said Monday he was not aware of the book’s release. When asked of Rother’s assertion that the case was a mess, he said: “She is entitled to that interpretation, but clearly the jury concluded otherwise.”

This is the 15th book from Rother, who was a reporter at The San Diego Union-Tribune from 1993 to 2006. Now a New York Times bestselling author, her other true-crime works include looks at the cases of a San Diego toxicologist convicted of poisoning her husband; the 2011 death of a woman in Coronado’s Spreckles mansion; and the rapes and murders of two teens a year apart in North County by the same man

The 2010 disappearance of Joseph McStay, 40, Summer McStay, 43, and sons Gianni, 4, and Joey Jr., 3, grabbed local and even some national attention, not just from news outlets but also from followers of true crime and computer sleuths.

McStay ran a business selling interior water features. He often hired Merritt, a talented welder, to craft them.

The McStay family moved from Orange County to Fallbrook in late 2009. They disappeared in early February 2010.

After a lengthy investigation, San Diego County sheriff’s detectives came to suspect the family had traveled into Mexico — among the evidence, their car was found near San Ysidro — and the case was transferred to the FBI in early 2013.

Then, in November 2013, the family’s remains were found. San Bernardino County sheriff’s detectives took over the investigation. A year later, Merritt was arrested and charged with murder.

Rother said she started looking at the McStay case early on — “You don’t see entire families go missing, especially with little kids,” she said — and was in the courtroom for Merritt’s 2015 preliminary hearing.

It took until 2019 for the case to reach trial, and it ran for several months. Prosecutors alleged Joseph McStay had been giving less work to Merritt and also suggested Merritt had dipped into one of his business accounts for roughly $20,000. They argued that the McStay family was killed in their home, then taken to the desert for burial.

But there was no blood found in the home or Merritt’s truck, the defense argued. They argued that no DNA or blood tied Merritt to the killings. They told the jury that prosecutors had nothing more than a supposed motive and argued that evidence had been misconstrued or ignored.

“I don’t take a position on whether Chase Merritt killed the McStay family,” Rother said. “I just lay out the evidence and let the reader decide.”

Merritt was convicted of murder and sentenced to death in 2020. However, with California’s death row now closed, he is incarcerated at Richard J. Donovan Correctional Facility, a state prison located in Otay Mesa.