In one episode, Mac and Flack are caught in a bomb blast in a building while trying to evacuate it. Though he himself is wounded in the neck, Mac is able to stabilize a critically injured Flack long enough for help to arrive, thanks to his previous traumatic experience in the Beirut barracks bombing. Mac and his team discover the NYC bomber to be a schizophrenic would-be Marine out to prove the vulnerability of the city to terrorist attack. By appealing to the man's sense of military duty, Mac is able to get him to surrender. The detective privately acknowledges to Stella that, while the bomber's methods may have been flawed, Mac could not argue against the principle of protecting his city and country. After the resolution of the crisis, Mac and the other CSIs stay by Flack's hospital bedside in shifts until he recovers.