Police investigating the disappearance of two children in Idaho last year have found what they believe to be human remains.
Joshua "JJ" Vallow, who was then seven, and his sister Tylee Ryan, 17, have not been seen since September 2019.
Their mother, Lori Daybell, was arrested in Hawaii in February.
The remains were discovered at the home of Mrs Daybell's current husband, Chad Daybell, but have not yet been identified.
Mr Daybell was taken into custody on Tuesday in Rexburg, Idaho, police said.
He is an author who has written several apocalyptic novels loosely based on Mormon religious teachings, and the couple have been involved in a group that promotes preparing for the apocalypse. The organisation, Preparing A People, has denied being a "cult".
Three suspicious deaths have also been linked to the case.
The children's mother Lori moved to Idaho from Arizona in late August 2019 after her then-husband, Charles Vallow, was shot dead by her brother, Alex Cox.
Cox claimed the shooting had been in self-defence. He died of unknown causes in December.
Lori then married Chad Daybell in October, just two weeks after the death of Chad Daybell's wife Tammy.
According to her obituary, Tammy Daybell died of natural causes, but police ordered that her body be exhumed after Mr Daybell's quick remarriage.
In November, police were called by the grandparents of one of the children to check on the family at their home in Rexburg. Officials say they later learned that Joshua "JJ" Vallow and Tylee Ryan had not been seen for months.
Authorities say Mrs Daybell gave misleading answers to investigators' questions and outright lied about their whereabouts and even their existence. She left town the following day. Authorities searched a nearby storage unit, and found clothes and toys that appeared to belong to her children.
She was arrested in Hawaii on charges including child abandonment and contempt of court in February, after missing a January deadline to deliver her children to authorities. Police at the time warned that the children were in danger.
According to divorce documents filed by her late husband, Charles Vallow, before his death, Mrs Daybell believes she is "a god assigned to carry out the work of the 144,000 at Christ's second coming in July 2020".
She also allegedly threatened to kill him if he got in her way, claiming she had "an angel there to help her dispose of the body". He took out a protection order following the threat, court documents show.
He described her as "infatuated and, at times, obsessive about near-death experiences and spiritual visions", and said she refused to see a therapist because "they would discover that she is a translated being".