|Season 3, Episode 4|
|Air date||October 11, 2010|
|Written by||David Grae|
|Directed by||Rob Bowman|
Beckett and Castle investigate a murder of a young executive involving antique guns, a 200-year-old bullet, and New York's steampunk subculture.
The episode ended with a tribute to author Stephen J. Cannell, a guest star throughout Seasons 1 and 2 who passed away on September 30th, 2010.
- Nathan Fillion as Richard Castle
- Stana Katic as Detective Kate Beckett
- Jon Huertas as Detective Javier Esposito
- Seamus Dever as Detective Kevin Ryan
- Tamala Jones as Dr. Lanie Parish
- Ruben Santiago-Hudson as Captain Roy Montgomery
- Molly Quinn as Alexis Castle
- Susan Sullivan as Martha Rodgers
- Andrew Leeds as Adam Murphy
- Ian Nelson as Troy Kenworth
- Ken Baumann as Ashley Linden
- Victor Webster as Josh Davidson
- Muse Watson as Ivan Podofski
- Thomas Kopache as Abe Sandrich
- Jim Piddock as Henry
- Ramon De Ocampo as Owen Peterson
- Randal Reeder as Roland D'Andre
- Eden Riegel as Rachel Goldstein
- Jen Lilley as Julia Foster
- Eugene Shaw as Joe
- Billy Atchison as Daniel Goldstein
- Lanie: How come you guys never bring me coffee? I’m here before you doing all the work.
- Castle: You can have the rest of mine.
- Lanie: Actually, I don’t drink coffee, but would it kill you to bring me a bear claw?
- Castle: 200 year old bullet can only mean one thing. Time-traveling killer.
- Castle: Unless time travel causes rust.
- Beckett: On your brain.
- Castle (referring to Alexis): I can’t believe she told you and not me. I’m supposed to be her go-to guy.
- Martha: Oh, darling, of course you are. It’s just, you know, it’s first love. It’s magical, ethereal ...it defies logic.
- Castle (to Beckett): Beckett, how do you know when you're in love?
- Beckett (to Castle): All the songs make sense.
- Alexis: Yeah. Being in love is exhausting.
- Castle: Yeah, You got that right.
- "Kiss Kiss Bang Bang" - Nitzer Ebb
- "Me You And Watson" - Alec Ounsworth
- Watch for: When Ryan and Esposito find the DeLorean, Javier calls it in to be towed. He gets the license plate number completely wrong (the plate is visible earlier in the scene). The car, while a DeLorean and quite cool, has changes that are nothing like that of the real Back to the Future car.
- This is the episode that everyone, including Castle, learns that Beckett has got a new boyfriend named Josh, the first since she dated Tom Demming and broke up with him. (A Deadly Game).
- In the end, when Castle comes home after meeting Beckett's new boyfriend, Alexis thanks him for the talk they had the other day. She says being in love is exhausting, Castle answers "You got that right" and looks away, like he's thinking of something (or someone) else.
- After his interrogation near run-in with the extremely powerful, scary suspect, Castle refers to him as "D'André the Giant", a tip of the hat to the Eighth Wonder of the World. The motif is continued by Esposito who asks, "Why did he go all "Hulk Hogan" on me?".
- This episode was in answer to a challenge from the steampunk community to produce a real "steampunk episode" after NCIS: LA's episode on the same subject. 
- When Castle and Martha are discussing Alexis' new love life, Martha says, "It's magical, ethereal,... it defies logic," a reference to Supertramp's 1979 single The Logical Song (although "ethereal" isn't in the lyrics).
- This episode concluded with a dedication to Stephen J. Cannell, which used the classic typewriter closing logo of his production company.