Someone has been ... but not who we're led to believe. Is Callen's father still out there? Or his mother?

Chris O'Donnell as G. Callen in the season finale of NCIS: Los Angeles. The team hunts down a woman with the key to a vast fortune - as well as Callen's own past.

Callen goes off the grid to end the first season of NCIS: Los Angeles after his identity is compromised. How will the events of this episode play out?

Sam and Kensi in the season finale of NCIS: Los Angeles. The show will be back for a second season in the fall - but will all its agents?

The season finale of NCIS: Los Angeles airs May 25, 2010. Here's a photo from the exciting conclusion to the first season.

We'll learn a lot about Callen in the first season finale of NCIS: Los Angeles. Where did this mysterious agent come from?