John Byrne, a courier, is shot dead whilst making deliveries. It emerges that one of the packages he delivered was fake, and evidently was sent to lure him to where the shooter was. The detectives discover that Byrne was cheating on his wife Adele with two different women, and she threatened to kill one of them. Adele is arrested after it's discovered she bought a gun out of state. Green is deeply upset when Briscoe announces he will be retiring.
Adele's gun is found, and turns out not to be the murder weapon. Briscoe and Green are led to the case of Randall Gardner; a very wealthy man killed just a few days before Byrne. His widow Belinda has inherited his multi-million dollar estate, and happens to own a coffee shop Adele frequents. Adele's gun is a match for Gardner's death, and the prosecutors conclude that she and Belinda agreed to kill each other's husbands to evade suspicion. Unable to prove conspiracy, McCoy is forced to put them on trial simultaneously since the case against Belinda would collapse if Adele were found not guilty.
Belinda is acquitted because she planted her gun on one of Byrne's girlfriends, thus introducing reasonable doubt. But Adele is convicted of Randall Gardner's murder, and McCoy convinces her that Belinda has set her up to take the fall. With Adele prepared to testify that Belinda essentially used her as a contract killer to murder Gardner, Belinda accepts a plea deal for 20 years to life. Green, Van Buren, and their co-workers say goodbye to Briscoe who is happy he won his final case as a detective.
This episode contains examples of:
- Brain Bleach: Briscoe needs some after checking a suspect's alibi:"Her alibi checks out, she was getting a bikini wax. It was called a Sphinx - don't ask. I wish I hadn't."
- A Deadly Affair: Adele wanted her husband dead because he was having affairs with two other women.
- Fall Woman: Adele is set up to be convicted by Belinda, while the latter is acquitted. She initially denies it, but McCoy is able to point out it was awfully convenient that her gun was recovered in the water with ballistics, while Belinda's was planted in another woman's workplace to create reasonable doubt.
- Gold Digger: Belinda Gardner is this and ultimately had her husband killed to get her hands on his money.
- Justice by Other Legal Means: Following her own conviction, Adele is willing to testify against Belinda in exchange for a deal on sentencing, but Belinda has already been acquitted of John Byrne's murder and can't be re-tried because that would be double jeopardy... so McCoy charges her with murder for hire in Randall's death, arguing that killing Adele's husband in return constituted payment for the purposes of the statute, and the judge, after considering it for a moment, decides to accept the premise. McCoy subsequently offers Belinda the same deal he'd given Adele, and she, seemingly realizing she's not going to get out of it this time, accepts.
- No-Tell Motel: The detectives briefly visit one of these where Byrne was known to take his girlfriends.
- Put on a Bus: This episode is the last one in the main Law & Order series with Lenny Briscoe, although he does show up in Law & Order: Trial by Jury.
- Screw the Rules, I Have Money!: McCoy convinces Adele that Belinda thinks this way and just used Adele to get out of a murder charge.
- Sexy Discretion Shot: In an attempt to identify one of Byrne's girlfriends, the detectives and an analyst watch security camera footage of Byrne making out (and more) with her outside a motel. The footage is not shown to the viewer, but everyone's comments indicate it was fairly graphic.
- Schmuck Bait: A variation. John Byrne is a package courier, so he is sent to deliver a fake certified letter to an address so Belinda will know he will show up eventually.
- Smug Snake: Belinda is incredibly smug when she points out to McCoy that the jury acquitted her. He doesn't care because she's going to jail anyway.
- "Strangers on a Train"-Plot Murder: What the episode's plot hinges on.
