In the second season of the show, Vance is introduced as the new Director of NCIS. He is later revealed to have a personal connection to Ari, who is the leader of a terrorist organization.
In the episode "Twilight," Vance and Ari meet in a parking lot to discuss a truce. However, Ari betrays Vance and shoots him in the face. Vance survives, but he is left with a permanent scar.
The scar on Vance's face is a reminder of the dangers of his job and the sacrifices he has made to protect his country.