Tessa Horton is found dead and strapped to the ceiling of her apartment by jagged wire. A symbol has been carved into her forehead. She appears to be the victim of a ritualistic murder. The killer took time to clean up, but there are prints on the doorway. Portions of Tessa's hard drive have been wiped clean. The victim's roommate says her friend was a shy girl who was seeing a mystery man. Shockingly, the prints found on the doorway are a match to our favorite mystery man: Richard Castle.
Beckett believes Castle must have touched the door when he first visited the crime scene, yet CSU claims the prints were there before he arrived. The victim's neighbor gives a description of a gentleman who visited Tessa the night she was killed. Her boss, Lloyd Kurtzman, matches the sketch artist's portrait. The team tries to link Kurtzman to a custom earring found at the crime scene. Too bad surveillance footage shows someone else buying the jewelry. The guy on the tape looks familiar. The guy on the tape looks a lot like Castle.
A mildly-freaked Beckett knows there has to be an explanation behind this latest lead. Ryan has no choice but to let Esposito in on the secret relationship their colleagues have recently struck up. As for the case, things are looking bad for Castle when his friends show up at his place with a search warrant. They traced the jewelry purchase back to him through his financial records. They also find physical evidence linking him to the murder of Tessa Horton. Castle is cuffed and placed under arrest.
Wire and hooks like the ones used to bind the victim are found in one of Castle's carrying bags. There's also a shirt covered in blood that matches the victim's. Beckett says, "The evidence isn't the whole story. Castle taught me that." Even Captain Gates has trouble believing Castle could be involved in such a heinous crime. Now that her colleagues know about her relationship with their prime suspect, Beckett lets Ryan and Esposito know that Castle wanted to be alone to write during the time of the murder. In other words, he has no alibi.
Alexis and Martha assure Beckett that no one else could have access to their apartment. Beckett assures Castle that she will get to the bottom of what's happening. He knows this. Unfortunately, the evidence continues to mount. A deleted file from Castle's computer shows an outline of a story. It's all about a killer who stages a crime scene that's so bizarre that the cops can't see he's hiding right under their noses. There are also dozens of emails suggesting Castle was having an affair with the victim.
Tears stream down Beckett's face as she lays everything out to Lanie. She says, "I know him, Lanie. He is an immature, egotistical, self-centered jackass sometimes, but he's not this." As for Castle, he is visited by someone he knows all too well while in his holding cell. Serial killer Jerry Tyson, aka "3XK," stands before him in a police uniform. All that's happening right now is his doing. Tyson has people waiting to murder Castle when he's moved to central booking. He'll be killed in prison and there's nothing Beckett can do to stop it. That's how Tyson will get his revenge on the both of them.
Beckett lets Castle know that she never stopped believing in him. Still, she can't convince the D.A. to delay the transfer out of the precinct. Officers arrive to take their prisoner away. Castle says he would give anything to be at the first place Beckett ever handcuffed him: The New York Public Library. Then he's led out of the station by two uniformed cops, who are later deemed to be imposters. The fear is that Tyson now has Castle in his clutches, but the District Attorney is calling this a prisoner escape.
The manhunt is on for Castle, but Beckett knows exactly where he is. She understood his message back in the holding cell. Castle is waiting for her at the New York Public Library after successfully orchestrating his own prison break. They realize the man who bought the earrings was a celebrity impersonator hired by Jerry Tyson. They ultimately track down the building where Tyson was holed up. Inside, they find the materials he used for the frame job. It's more than enough to clear Castle for the murder. But Tyson is nowhere to be found.
While stuck on a bridge, Castle thanks Beckett for believing in him. Then... SMASH! An SUV plows into them. BANG! BANG! BANG! Gunshots rip through the car. It's Tyson. Beckett fires back hitting the killer in the chest. But Tyson's wearing a bulletproof vest. He's able to overpower Beckett. He wants Castle to watch as he kills her. BANG! BANG! BANG! Castle shoots Tyson multiple times until he falls off the bridge and into the water. They don't recover the body. Castle believes Tyson is still alive. This was all part of his plan to disappear again. This isn't the last he's seen of the Triple Killer.