"Kate is smart, charming, and wise for her years," says executive producer Erica Messer. "Her background is criminal psychology, and her passion comes from wanting to make the world a safe place. She's had a lot of personal loss that makes her a patriot and a nurturing figure to those in her personal and work families."
Callahan, an eight-year FBI vet, is also an old pal of the BAU team and fits right in — just like Hewitt does on set. "The rapport feels like friends catching up," Messer says. "If feels like she's always been here."