NEW YORK (AP) — For the first time, “Dateline NBC” is trying to stretch its true crime franchise into a multi-part series. “The Widower,” about a Las Vegas man who had four of his wives die under mysterious circumstances, will debut on Feb. 18 and unfurl over five hours on three different nights. It’s a nod to series like HBO’s “The Jinx” and Netflix’s “Making of a Murderer,” popular crime stories that had multiple parts. In an effort to expand its appeal, “Dateline” will start a dedicated channel on the Peacock streaming service later this month and debut its second-ever podcast with Keith Morrison as narrator.