Aaron Cooper is essentially the catalyst for events in "Embassy Row", since he calls Chance's 'family and friends number', given to him by his brother, Danny. Aaron is in grave danger, and since Danny returned under heavy fire in Bosnia to get a wounded Chance out, this debt is one with no price tag or limits. Danny, a former intelligence officer, was into something big, and in deep, and the bad guys believe little brother knows all about it, hence the 'death mark'.
He is portrayed by Sean Maher.