On the night of his disappearance, popular local musician Scott Sessions arranged a date with mother-of-three Heather Frank at her house in the small town of Greeley, Colorado. When authorities found Sessions’ body at a campground days later, they set their sights on Frank as the prime suspect. But when Frank goes missing, the police realize that an ex-boyfriend’s jealousy may have turned deadly. A new “20/20” reports on how covert police surveillance uncovered two horrific murders and exposed a killer.