Several characters attempt unsuccessfully to help an amnesiac Gibbs regain his memory as only he knows the details to an impending terrorist attack . Shepard contacts Gibbs ' NCIS mentor and former partner , Mike Franks ( Muse Watson ) , for assistance . He is partly successful , as Gibbs remembers working with Franks and learning from him , recalling up to the point that Franks retired after his warnings about an upcoming terrorist attack were ignored , resulting in the Khobar Towers bombing . Franks fills him on what has been happening in the world since 1991 , and the shock of learning of the September 11 terrorist attacks causes him to become physically sick
Khobar Towers bombing
Khobar Towers bombing
Hiatus (NCIS)