"Devil's Trifecta" is the ninth episode of the tenth season of the American police procedural drama NCIS, and the 219th episode overall. It originally aired on CBS in the United States on December 11, 2012. The episode is written by Steven D. Binder and directed by Arvin Brown, and was seen by 17.65 million viewers.
Diane, the ex-wife of Gibbs and Fornell, returns in the middle of an NCIS investigation.
Late one evening, whilst at a Drive-thru, FBI Agent Tobias Fornell is attacked. He is shot at while in his car, only to return fire and kill the shooter.
The next morning Fornell has called in Gibbs and his team, who are working the crime scene. Fornell reveals he was wearing a bullet-proof vest and claims to have never seen the shooter before, who is revealed to be a Navy Seaman Tyler Brown. The team rule it out as a crime of opportunity when they find a piece of paper with Fornell’s licence number on it, proving he was targeted. The paper leads them to a bar where Brown worked as a bouncer.
At the bar they run into their mutual ex-wife Diane, who claims to be there conducting an audit for the I.R.S. After the bartender lets slip that she was looking into buying the bar and using the name ‘Mrs Fornell’, they arrest her (pointing out to the team that she lied to federal agents and used a false name). They insist DiNozzo conducts the interrogation, which is cut short by the director.
The I.R.S Deputy Commissioner called Director Vance to confirm that Diane was, partially, telling the truth. She had gone back to work for the I.R.S, but had been promoted to a G.S 11 position in the Criminal Investigations Division. She had been undercover at the bar (using her old I.D from her marriage to Fornell due to ‘budget cut’) because the bar is believed to be a front for an identity theft operation. The Director then tells them that Gibbs, Fornell and ‘Agent Sterling’ will be working on the case together.
After deciding that the attempt on Fornell’s life was due to Diane using her old I.D, the team realize that Brown was working in the scheme as muscle. Their first suspect as the brains is an accountant named Oliver Lambert. When they raid his house they find a number of freezers, one of which contains the body of a man who frequented the same bar Brown worked at and was also involved in the scheme.
After Lambert himself (who was helping smuggle the fake IDs to enemy Asia inside fish shipments) turns up, only to end up dying from stab wounds, they realize the real killer is Gordon Freemont, one of Lambert's clients and that he was actually running a smuggling operation. They catch up to him at a wedding reception, where he tries to kidnap Diane, which Gibbs averts by delivering a fake proposal to his ex-wife.
A subplot of the episode is the way Diane interacts with the team. She tells Ziva she is taking a break from her husband, but let’s slip to McGee that he is leaving her. She and McGee also fall asleep while talking, so rumors circulate they slept together, infuriating Fornell and amusing DiNozzo. Fornell also tells Gibbs that Diane specifically requested transfer to his jurisdiction.
The episode ends with Gibbs telling Diane to give her current husband a break or she’ll turn into him. They discuss how they are both looking for the right person and Diane asks Gibbs how he feels about living his life alone, too which he replies "I’m not alone."
"Devil's Trifecta" is written by Steven D. Binder and directed by Arvin Brown. The episode marks the return of Gibbs' ex-wife Diane Sterling (Melinda McGraw), first seen in the season nine episode "Devil's Triangle". On October 16, 2012, TV Line reported the return of both Diane Sterling and Tobias Fornell (Joe Spano), where Sterling "has to work undercover" with Gibbs and Fornell".
In Diane's first episode she came to Gibbs and Fornell for help finding her missing husband, but in this episode the writer wanted to "put her on more even footing - to even make her an equal, if possible. [...] The thought of her throwing a badge in Fornell’s face was too good to pass up."
"Devil's Trifecta" was seen by 17.65 million live viewers following its broadcast on December 11, 2012, with a 2.8/8 share among adults aged 18 to 49. A rating point represents one percent of the total number of television sets in American households, and a share means the percentage of television sets in use tuned to the program. In total viewers, "Devil's Trifecta" easily won NCIS and CBS the night. The spin-off NCIS: Los Angeles drew second and was seen by 15.12 million viewers. Compared to the last episode "Gone", "Devil's Trifecta" was down in both viewers and adults 18-49.
Mary Powers from TV Fanatic gave the episode 4.7 (out of 5) and stated that "If there is an episode that features Gibbs and Fornell, you can almost guarantee it to be a hoot-feast, and tonight's episode was no exception. As serious as the episode began with Fornell almost being killed, it quickly turned into one laugh right after another when the center of the entire mess turns out to be Gibbs and Fornell's mutual ex-wife, Diane Sterling (Melinda McGraw)."