So far NCIS: Los Angeles has focused heavily on the backstory of Chris O'Donnell's G. Cullen.

While this character will remain prominent through the fall, executive producer Shane Brennan teases to TV Guide that developments for Kensi and Sam are on the way.

"If Callen is a mystery, then Sam is an intrigue," Brennan said. "There is one stunning revelation about Sam Hanna that the audience will go, 'I did not see that coming.' It's amazing. I won't tell you when it's coming, but it will arrive with some impact."

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.