Sam Fisher's "handler." His role in the game is to guide the player through each level over the cochlear implant radio, providing information such as critical updates, objective and thus changes, and enemy status.
Splinter Cell: Conviction
In Splinter Cell: Conviction it is revealed that Lambert's life ended in Double Agent as he is shown being shot by Fisher. It's also revealed that Lambert tricked Sam into joining the JBA by faking the death of his daughter. He was succeeded by Tom Reed.