Being responsible for a successful show such as Tracker comes with its challenges - and has kept star Justin Hartley too busy. "He lives and breathes Tracker," Hartley's costar Fiona Rene exclusively told Us Weekly at CBS Fest on Wednesday, April 15. "We were joking around the other day. He was like, 'I used to have a life. I used to have friends.'" Rene praised Hartley's devotion to his job. "What I've learned specifically is his attention to detail while we're shooting," she added.