Agent Callen's Past to Be Revealed on 'NCIS: LA'

The past of Chris O'Donnell's NCIS: Los Angeles character is shrouded in secrecy, but tonight some of those mysteries will be unveiled.

Hetty (Linda Hunt) finally has a sit-down with Special Agent Callen (O'Donnell) in the show's next episode, giving Callen details about his mother that have been kept from him all these years.

Watch the clip to hear the bombshell revelation that Hetty drops on Cullen, and tune in to NCIS: Los Angeles tonight on CBS to view the entire must-see episode.