About NCIS: Los Angeles Season 1, Episode 24 : Callen, G

The NCIS team locates Eugene Keelson's hideout filled with dossiers on Callen and other individuals in the intelligence community (including Hetty). Someone knows they are in the house, and destroys it in an explosion, along with the computers and all hard copy files except for one. From the one recovered file, Callen finds evidence of his long lost sister.