(NBC News) — Tonight, “Dateline” investigates the case of two Idaho children, JJ Vallow and Tylee Ryan, who vanished last September. This two-hour broadcast will take you across five states and more than 5,000 miles.

It is the first comprehensive primetime special on this bizarre mystery making national headlines.

See exclusive footage of “Dateline” tracking down the children’s mother, Lori Vallow and her new husband Chad Daybell, at a Hawaiian resort just days after they were questioned by the Kauai Police Department.

Keith Morrison describes it as “a mystery, unlike anything we’ve ever seen.”

Watch “Dateline” tonight on NBC4 starting at 9 p.m., right after “Lincoln Rhyme: Hunt for the Bone Collector.”