<P> Carrie Clark (Salli Richardson - Whitfield) is a lawyer and a former Special Agent with the FBI . She worked on FBI Special Agent Tobias Fornell's team, now a criminal attorney . She appears in season 11 episode 8 "Alibi", season 12 episode 8 "Semper Fortis" and season 13 episode 9 "A Day in Court". She has worked with Gibbs and his team on a case, while working for the FBI (off screen). She first appears in episode Alibi, after Marine Staff Sergeant Justin Dunne, is arrested, Dunne requests an attorney, and hires former FBI agent Carrie Clark, who also happens to be an old acquaintance of the team . Dunne tells Carrie that he has an alibi, in that he was involved in a murder outside of the base at the time of the hit and run, and that somebody else must have stolen his truck . Due to attorney - client privilege, Carrie cannot tell Gibbs and the team anything about Dunne's crime other than he has a solid alibi . However, she manages to leave small, subtle clues for the team to follow . </P> <P> Lieutenant Jonas Cobb (Kerr Smith) is the real name of the "Port - to - Port Killer", or' P2P' for short, the primary antagonist of season eight . Originally recruited into a CIA assassination team code - named Frankenstein, Cobb cracked under intense and inhumane training before escaping . He re-surfaced in Rota, Spain, where he began his pattern of killing Navy personnel when they made landfall . He has also killed victims in Guam, Japan, Norfolk, Washington, D.C and was in the process of killing another victim in Hawaii before being interrupted by CIA operative Trent Kort . A ruthless serial killer, he is responsible for the deaths of Mike Franks and NCIS Agent Gaven Levin (the latter one he fatally shoots with Franks's own gun instead of using a knife), and takes NCIS agent E.J. Barrett hostage . One body in the episode "Baltimore" resembles P2P's work, but is later found to be a copycat by Dr. Mallard because of the way the knot is tied . The killer is revealed to be Agent DiNozzo's former superior at Baltimore PD, and the victim is DiNozzo's former partner there, with whom he never got to reconcile . The real P2P, though not known to be Cobb at the time, makes the deception final through a fake Abby Scuito email . Cobb's modus operandi involves luring his victims into a trap before slashing their throats from behind . He then scrubs the body down with a hospital - grade cleanser before wrapping the bodies in plastic and dumping them in isolated areas . He has been known to dress seamen in the uniforms of officers, and often leaves personal effects of his victims behind frozen in ice that foreshadow his next kill, though his m.o. changes forever in "Swan Song". Psychological profiling of Cobb depicts him as methodical, intelligent, and opposed to authority, but not easily distracted by law enforcement . The threat posed by Cobb is deemed so great by Director Vance, that he deliberately changes NCIS policy to antagonize Gibbs in the hopes of setting Gibbs up as a figure Cobb will identify with, in an attempt to lure Cobb into a trap . Cobb, after abducting Ziva David, gives himself up to NCIS in order to start the next phase of his plan . While Gibbs interrogates him with Agent Barrett watching, he tells a story about the son of a Marine who was told that he had to have his horse put to sleep, which turns out to be a deadly seed planted into Cobb as a child, since the story was about him anyway . Cobb is killed in the season eight finale, "Pyramid", where it is revealed that everything he had done since his first kill in Rota has been a part of a larger plan to get revenge on those he holds responsible for Operation Frankenstein--Leon Vance, Trent Kort and the Secretary of the Navy . He is aware that what he does is evil, but maintains that his actions have been for the greater good . He is shot and killed by Gibbs and Vance when he refuses to surrender . In death, he is said to have had a smile on his face while his corpse lay on a wrecked car . </P> <P> Jonathan Cole (Scott Wolf), alias FBI Agent Casey Stratton, is one of the primary antagonists of season nine . He was formerly a member of "Phantom Eight", a clandestine team of operatives assigned to the Watcher Fleet tasked with protecting the United States Navy . Cole goes rogue some time after the Phantom Eight are disbanded and begins working with Sean Latham, the corrupt Director of Special Operations for the Office of Naval Intelligence and a former member of Phantom Eight himself . Cole and Latham conspire to sell a series of microchips belonging to Phantom Eight members, which give their owners unrivalled access to the Navy mainframe . Cole makes his first appearance in "Nature of the Beast", where he adopts the alias of Casey Stratton, an FBI Agent assigned to investigate a shooting involving Tony DiNozzo . DiNozzo, having forgotten the events that led up to the trauma of the shooting, attempts to reconstruct his memories, recounting his investigation of NCIS Agents Simon Cade and E.J. Barrett . His investigation centers on a microchip Barrett extracted from the body of Gayne Levin, who also served in Phantom Eight, but wound up the last murder victim of Lt. Jonas Cobb, the Port - to - Port Killer . Cole manipulates DiNozzo, Barrett, and Cade into first distrusting one another and then meeting, where he attempts to kill all three before fleeing with the microchip . Cole kills Cade, wounds DiNozzo, and misses Barrett, who flees . He later approaches DiNozzo in the hospital under the Casey Stratton alias, but is unable to kill him as DiNozzo is under guard . Cole reappears in "Housekeeping", where he attempts to kill E.J. Barrett, who has since resurfaced . After the first failed attempt, Latham advises Cole to abandon his mission, but Cole refuses, claiming that he has to see it through, and he murders Latham . Now aware of his role in Phantom Eight and his actual name, NCIS trick Cole into attacking a safehouse under the pretense that Barrett and DiNozzo are hiding there . The safehouse is empty, and Cole is apprehended . His final appearance comes in "Till Death Do Us Part" when Gibbs feels he would be an ideal operative to get close to the terrorist Harper Dearing . Cole agrees in exchange for a (slightly) reduced sentence, but Dearing is already aware of his role and rejects his offer of help . Cole is killed when attempting to defuse a bomb left by Dearing outside NCIS headquarters . Although Cole never offers a reason for his crimes, and the circumstances that led to his becoming a traitor are never detailed, he does admit that he thought he had good reasons for doing what he did; he was soon proven wrong . </P> <P> Dr Grace Confalone (Laura San Giacomo) is the therapist of both Gibbs and Dr. Cyril Taft . First appearing in "Loose Cannons", Grace builds a professional relationship and personal friendship with Gibbs, nicknaming him "Popeye", and often resorting to child psychology (including picture charts) to tap into his psyche . In "Family First", Grace befriends Emily Fornell at the request of Gibbs. Grace returns in "Privileged Information", as Gibbs investigates a patient of hers, a Marine Sergeant, after she ends up in a coma, and tells Gibbs he should treat it as a murder investigation, but cannot divulge further due to doctor - patient confidentiality . When the patient dies, Grace tells Gibbs that the patient was involved in covering up a murder, but that she didn't tell her any details . In "Twofer", following Gibbs' and McGee's return to the US after a failed mission in Paraguay, Grace is appointed to conduct psychiatric evaluations on them to determine whether they are fit to return to NCIS . Gibbs surprisingly is able to open up to her about his troubles more than she's already known, but McGee skips his appointment with her, frustrating her . Gibbs is able to convince McGee to go to his appointment with Grace, and meets with McGee outside her office after the session, having himself become a more regular patient of Grace . </P>

Who plays ducky's assistant casey on ncis