The body of a dead man flies down a garbage chute in an apartment building. The victim was Sam Parker, a suburbanite from Connecticut who wound up with a bullet hole in his chest. At the morgue, Beckett and Castle start to question the woman weeping over the victim's body when another woman comes in claiming to be the dead guy's wife. The first woman says she's his fiancee. Uh oh.
Sarah Reid, the fiancée, knows the victim as Jake Holland. He's a co-worker she met six months ago who lives in the city and spends his weekends visiting his sick father upstate. Or so she thought. Helen Parker, on the other hand, is Sam Parker's wife of ten years. She tells Castle and Beckett that Sam left his job at Connecticut Solutions six months ago and took a job in the city with New York Recycle. The commute was so tough that he took an apartment in the city, but he'd come home to visit her and the kids every weekend.
Lance Carlberg, the CEO of New York Recycle, says that he should have known "Jake Holland" was too good to be true from his resume, but he called all the references himself and got glowing recommendations. He also confirms that he knew Sam (aka "Jake") was engaged to Sarah Reid, and that there was never any reason to believe they were less than completely happy.
Thinking the wife knew about her husband's affair, Beckett and Castle confront Helen, but she claims Sarah is the one who knew about Sam's double life all along. As proof, Helen cites multiple hang-ups in the past month and the fact that Sarah had the number to call recently to ask for funeral details. She also asked for the return of a pen she had given Sam that was a family heirloom.
Castle and Beckett discover that Sam was planted at New York Recycle as a corporate spy. Sam was sending complex chemical formulas to Andy Berman, the CEO of Connecticut Solutions. When Berman called Sam the night of his murder, Sam claimed to have the secret to New York Recycle's battery recycling technology.
Sarah Reid is caught snooping around Helen Parker's place. She claims she was looking for her grandfather's pen. Meanwhile, Esposito and Ryan discover Sam was going to a series of odd places: a house on Long Island, a processing plant in Paramus and the port in Newark. We're not sure what the other stops were about, but the house on Long Island belongs to Lauren Branston, who is really "Jake's" fiancee, Sarah Reid!
When Lance Carlberg realized that Sam was a spy, he hired Sarah to feed him false information. Sarah fancies herself quite the secret agent until Castle and Beckett inform her that Sam was hip to her game. Beckett theorizes that Sarah killed Sam when she realized her cover had been blown and that Sam discovered New York Recycle's secret battery recycling process. Unfortunately, Sarah has plenty of witnesses to the fact that she was at her daughter's recital when the murder went down.
Castle realizes that if Sarah wasn't really in love with Sam, she wouldn't have given him her grandfather's pen. They head back to the Parkers' house to find some documents in the shredder. It was photographic evidence that New York Recycle's idea of recycling battery sludge involved changing the labels and dumping it in the ocean.
Beckett confronts Lance Carlberg with this evidence, but he refuses to talk. She suggests that Sam confronted Carlberg when he uncovered the ruse and that Carlberg shot him. The CEO claims she has no proof, but Beckett pulls out a revolver they found in the dumpster at Carlberg's building. It's a match for the murder weapon. Castle muses, "If only you'd recycled."
In a nice little side story, Alexis gets a temporary internship down at the station. Castle is happy to have his daughter nearby and Beckett is impressed by her dedication. Alexis comes across a photo album while cataloguing crime victim's unclaimed items. It takes some digging, but Alexis is able to track down the owner's daughter. Castle watches his little girl hands over the sentimental photos to the grateful recipient. Remember how we said Castle was happy to have his daughter working at the precinct? Well, he's still thrilled. But now he's also very, very proud.