NCIS: Los Angeles
executive producer Shane Brennan promises that Tuesday's episode will reveal more about the mysterious past of Chris O'Donnell
's Agent Callen than the first two seasons combined.Fall Preview: Get scoop on all your favorite returning shows
"This is a moment that we've been planning for 50-odd episodes," Brennan tells TVGuide.com. "In the first four or five minutes, you will learn an enormous amount of detail about who Callen ...