Projížïka mladého páru na horských kolech končí nečekaně ve chvíli, kdy mladík padá i s kolem do rybníka. Když se vynoří, vedle něho na hladině plave mrtvola mladší ženy se střelným poraněním. Jde o Carrie McLellanovou, která pracovala pro Pentagon. Vzápětí se Gibbsovi ozve jeho dávný přítel senátor Kiley, a přiznává se, že měl s Carrie poměr. Protože však potřebuje prosadit ještě jeden důležitý zákon, prosí Gibbse, zda by mohl zveřejnění jeho jména oddálit. Gibbsův tým však s případem postupuje poměrně rychle a Gibbsovo nestandardní chování vzbuzuje podezření.

V důsledku toho pak Gibbs seznamuje ředitele NCIS Vance s Kileyem a s tím, že se zřejmě na něho kdosi pokouší shodit vinu za smrt Carrie...

In the Squadroom: Ziva presents Abby with a cupcake, and thanks her for letting her sleep at her house the previous night. Tony gets a little jumpy and asks for further details on their night together. He asks McGee who tells him to stay out of it. Gibbs then comes in and says that a female naval Lieutenant Commander was found dead in the park. The team then grab their gear and head out to the park.

At the Park: Ducky realizes that the victim was shot in the back and bled out on a solid surface, he says that he will know more when he gets her back to autopsy when it begins to show signs of a storm coming soon. As Ducky races to beat the storm, Gibbs gets a phone call and races away from the scene, leaving Tony and Ziva to wonder what he's up to.

Along The River: Senator Kiley talks to Gibbs about his connection to the dead Lt. Cmdr. and admits that he was having an affair with her. He says he's coming forward because he realizes that the evidence would point to him and he believed that someone was trying to frame him. He asks Gibbs to leave his name out of the case so that a bill he is working on can be passed, but Gibbs says he'll see what he can do.

In The Victim's House: Tony and Ziva find evidence that she was having an affair with a married man, and become suspicious when they notice that he does not sign his name or have pictures anywhere in the house. They notice a birthday card in which the man signed "you know who" instead of his name. Gibbs then walks in and they brief him on what they found.

(Quick revelation of what happened until someone finds time to complete this properly:
Gibbs' connection to the Senator means that he behaves oddly in the eyes of the A-Team.
A visit to the Senator's house let's us meet his chief of staff who is as loyal as a St Bernard to the Senator.
The Senator's wife comes to see Jethro at his house (she knows the doorbell never works, that the door is unlocked and that he will be in the basement and she knows to ask for hard liquor. The conversation reveals that she and the Senator (who was once the rookie Lieutenant that Gunny looked after, and whose Dad was known to Gibbs) were "there for Gibbs" when Shannon died (We all find this very hard to believe: they are not Gibbs' type of people, but it gives a reason for her to visit the basement and speak 'off the record').
She swears to Gibbs that her husband is not the sort of man who could shoot someone in the back. Gibbs sends her home to her hubby whom she has been avoiding. She knew about the affair all along.
All evidence is pointing to the Senator, including faked voicemails to the Director's voicemail box, which McGee is asked to analyse: he discovers it is an automated voice. (You type in the words on the computer and it reads them out).
The gun had been found by McGee and DiNozzo, in the waste water ditch near the scene of the crime (McGee fell in and on top of the gun. He found it with his posterior.)
The voicemails allude to the gun and ask why the Senator has not been arrested: it looks like a frameup.

Meanwhile, back in the mysterious world of Sciuto, our Princess of the Dark Side has been using her forensic skills to gather evidence as to who stole her cupcake. She collects crumbs off Gibbs coat (he is astonished), she creates a crime-scene (complete with tape) in her lab (the cake was in her fridge). She creates a photo wall of suspects (which Gibbs is astonished to see includes not only Gibbs but also the night janitor...which Abby says is on the grounds that he has put on weight lately (but there hasn't been a night yet for the guy to come to work, find the cake and steal it.). This sub-plot continues throughout the episode. Abby collects mouth swabs from all the Giblets, including Ziva who gave her the cake in the first place. She also dusts for fingerprints. She cunningly works out whodunit...revealed later.

Back to the main story: as you suspected, there is a twist: the Senator's chief of staff is found dead, with a plastic bag over his head, diazepam in his system, a suicide note and the appropriate stuff to have made the fake calls.
The Senator happens by the crime-scene and talks to Gibbs.
Director Vance tells Gibbs that the Senator is going to make a press statement in 2 hours. Vance gets the feeling that Gibbs is unconvinced by the murder then suicide picture that they have been given. Gibbs says 2 hours is a lot of time to solve a case and pursues it.
Finally we see Gibbs attend the press conference at the Senator's house with Vance, but instead of supporting, he tells the Senator that he wants to arrest him. The Senator confesses but Gibbs isn't buying it. He challenges the wife and points out that she knew the lover was shot in the back, which is a detail not revealed publicly. She could only know if she did it. She confesses that it was a moment of madness. Gibbs points out that staging the suicide of the Chief of Staff was coldblooded murder. Gibbs is not minded to spare the couple the walk of shame to the police cars. The arrest is captured on TV.

Meanwhile, Abby has solved her case and confronts...McGEE! Who vehemently denies wrongdoing by pointing out that he would never leave a fingerprint at the crime scene because he knows that Abby would be able to check it. And she agrees: there was no fingerprint in the fridge but there was only one fingerprint on the new box of latex gloves other than Abby's own print. McGee used the new box of gloves to cover his hands in order to steal the cake. He gets headslapped by Tony and Ziva but Abby asks "How was it?" and he makes her drool. She is then mad but Gibbs walks in and says 'get over it'.

Final scene: Director Vance and Gibbs watch that walk of shame on the evening news, in the Director's office. Gibbs is looking mighty depressed (he dislikes breach of trust and acts of disloyalty). Director notes this and when Gibbs says that loyalty is crucial, Vance asks how does Gibbs see their own trust and loyalty? Gibbs just stares. )