The latest clue in the investigation of doomsday couple Lori Vallow and Chad Daybell is a weird email sent in her previous husband’s name shortly before he was shot dead.

Investigators want to question Vallow and Daybell about the June 29 message as they try to put together pieces of a puzzle that includes two dead spouses, two missing children, and an obsession with the apocalypse and near-death experiences, KSL-TV reported.

Vallow’s 17-year-old, Tylee Ryan, and adopted 7-year-old, J.J., have been missing since September—and the search for them has also raised questions about the deaths of Vallow’s ex, Charles Vallow, and Daybell’s wife, Tammy.

Charles Vallow, 62, was killed by his wife’s brother, Alex Cox, during what was initially described as a domestic dispute on July 11 in Chandler, Arizona.

Two weeks earlier, Charles wrote an email to another brother-in-law, Adam Cox, in which he claimed that Lori had created an email account in his name and used it invite Daybell, who lived in Idaho, to visit him in Arizona.

“I would gladly fly you down here early next week,” the bogus invite read. “You could stay in our guest room like before. I hate to take you away from your family, but I would definitely make it worth your time.”

When Charles got wind of the email, he questioned Lori about it but got no answers.

“I’m not sure of the relationship with her and Chad Daybell but they are up to something… She will not explain it…” he wrote to Adam Cox, according to KSL.

“I am going to send it to Chad Daybell’s wife. Her name is Tammy and I found her email address on their website too… I’ve got her cell number too.”

It’s not clear if Charles ever contacted Tammy. And three months after he was killed, she was dead, too. Weeks later, Lori and Chad—who bonded in a doomsday prepper group—got married.

Sgt. Jason McClimans of the Chandler, Arizona, Police Department called the email “suspicious.”

“It draws various questions that we would need to ask Lori and Tylee and possibly Chad to get to the bottom of it,” he said.

There’s no shortage of questions police want to ask Lori, 46, and Chad, 51, starting with the location of Tylee and J.J., the only other witnesses to Charles’ death.

Idaho police say Lori refused to cooperate with search for the children, lied about their whereabouts, and took off for Hawaii with Chad when they started investigating.

A judge ordered her arrested for desertion and contempt, and she is being extradited from Hawaii to Idaho to face those charges. Her new husband has reportedly already returned to Idaho.

Police have reopened the investigation into Tammy Daybell’s Oct. 19 death and exhumed her body, and they are taking another look at Charles Vallow’s killing and the unexplained December death of Alex Cox. They are also investigating an October incident in which someone driving Charles’ car took a shot at Brandon Boudreaux, the estranged husband of Lori’s niece.