The investigation started roughly 29 months ago with two missing children. It soon grew to encompass five states, four suspected murders and claims of unusual, doomsday-focused religious beliefs involving “dark spirits” and “zombies.”

On Monday morning, an Idaho jury will begin the difficult task of deciding the veracity of those claims and others in the triple murder trial of Lori Vallow Daybell.

Prosecutors charged Vallow Daybell and her husband, Chad Daybell, with multiple counts of conspiracy, murder and grand theft in connection with the deaths of Vallow Daybell’s two youngest children: 7-year-old Joshua “JJ” Vallow and big sister Tylee Ryan, who was last seen a few days before her 17th birthday in 2019. Prosecutors also have charged the couple in connection with the October 2019 death of Chad Daybell’s late wife, Tammy Daybell.

The investigation garnered worldwide attention and was closely followed in the rural eastern Idaho community where the bodies of the children were found buried in Chad Daybell’s yard. As a result, Seventh District Judge Steven Boyce moved the trial more than 200 miles west to the city of Boise.

Both defendants have pleaded not guilty, but only Vallow Daybell’s trial begins Monday. The cases have been separated, and Chad Daybell’s trial is still months away. Vallow Daybell faces up to life in prison if convicted.

In the hour before opening arguments were set to begin, television news crews and photographers stood outside the front of the courthouse as workers, jurors and onlookers made their way through a security point just inside the building.

The judge has banned cameras from the courtroom and the proceedings are not being streamed, but widespread interest in the case prompted court administrators to set up a separate “viewing area” to allow seating for media and members of the public. About 50 people were sitting in the viewing room.

Eighteen-hundred people were called as potential jurors, and the pool whittled down to 10 men and eight women last week.

All 18 will hear the case, but only 12 will actually take part in deliberations to decide Vallow Daybell’s guilt or innocence. The other six are alternates and will be released from service before deliberations begin. Jurors will not be notified they are an alternate until it is time for deliberations in order to ensure they all stay engaged throughout the trial.

The trial is expected to take up to 10 weeks.

Prosecutors say the Daybells espoused strange doomsday-focused beliefs to further their alleged plan to kill the kids and Tammy Daybell to collect life insurance money and the children’s social security and survivor benefits.

Police documents detailed interviews with friends and family members who said the couple led a group that believed it could drive out evil spirits by praying and that they sought revelations from “beyond the spiritual veil.” Vallow Daybell’s close friend Melanie Gibb told investigators that the couple believed people became “zombies” when they were possessed by evil spirits.

The group would spend time praying to get rid of the zombies and believed, if they were successful, the possessed person would physically die — freeing their trapped soul from “limbo.” Vallow Daybell called JJ and Tylee “zombies” several times before they died, Gibb told investigators.

Idaho law enforcement officers started investigating the couple in November 2019 after extended family members reported the children were missing. During that period, police say the couple lied about the children’s whereabouts. The children’s bodies were found buried on Chad Daybell’s property in rural Idaho.

The couple married two weeks after Chad Daybell’s previous wife died unexpectedly. Tammy Daybell’s death was initially reported as resulting from natural causes, but investigators had her body exhumed after suspicions grew when Chad Daybell quickly remarried.