McNally was by his side. "It's really, really lonely, yeah," she said.
Thorson's sister said the pair was always at each other's side, and they would even share the same plate at meals and read books simultaneously.
"Reading the same book, slowly, same page, waiting, and then turning the page," Alexandra Thorson said. "I don't know if you could call it intimacy. It was almost invasive. They had no personal space."
In 2010, Ian Thorson and McNally went off for a retreat at Roach's "university" in the remote Arizona desert. After saying goodbye, they settled in for three years, three months and three days of silent meditation. However, after a year and a half, the couple was asked to leave.
According to a letter Michael Roach posted on his website, Thorson and McNally were the subject of a "mutual spousal abuse" investigation after a medical practitioner at the "university" allegedly treated Thorson for three stab wounds inflicted by McNally. The letter said McNally claimed it was an accident and it happened when she was playing with a knife.
After leaving, the couple went to live in a cave in the Arizona desert mountains close to Roach's group.
But six weeks later, McNally called 911, saying she had an emergency. When medical crews arrived, Thorson was dead. Police did not suspect foul play. An autopsy revealed that Thorson died of dehydration and exposure and there was no evidence of stabbings. Police are not conducting a criminal investigation.
"This is a very inhospitable environment," said Sgt. David Noland, the Search and Rescue coordinator for the Cochise County Sheriff's Office. "The Indians did it thousands of years ago, but I haven't heard of anybody living out off the land in this area."
Thorson's mother said she is still in shock over her son's death and that Michael Roach's allegations of spousal abuse are exaggerated. She and Thorson's sister believe his death would not have happened if Roach had not asked the couple to leave the retreat.
"Getting them geared up for this retreat and then kicking them off is setting them up for a problem," Alexandra Thorson said. "That was irresponsible, I felt."
On his website, Roach wrote that he took the appropriate precautions before sending the couple off, offering them money, an assistant and a rental car to ease their transition. He said they refused his help and refused to tell anyone where they were going. Roach also wrote that he is deeply sorry for the family's loss, but Thorson's mother said this case should be a wake-up call for parents about the dangers of extreme religious groups.
"There's nothing good that can come for me personally because my son is dead," Kay Thorson said. "I certainly don't want this to happen to someone else."
Roach declined to grant "Nightline" an interview. He is holding a seminar on reaching enlightenment this weekend.
ABC News' Lauren Effron contributed to this report