As Castle and Alexis travel to London, their routine flight turns deadly when the plane's Air Marshal is found murdered. With the help of Beckett on the ground, Castle and Alexis race against time to find the killer before they carry out their fateful plan.
- Bait-and-Switch: The beginning of the episode has the airplane that Castle and Alexis are on experience turbulence, with the flight attendants looking worried. Knowing that the flight crew not smiling is a sign that something's not right, Castle decides to inquire them if there's a mechanical failure. This is where he instead learns that their flight's Air Marshall has gone missing, kickstarting his involvement in the episode's murder plot; meanwhile, the turbulence turns out to just be turbulence, and it dies down early in the episode.
- Body of the Week: Kyle Ford, the Air Marshall who was onboard Oceanic Flight 57, the same flight that Castle and Alexis are on. He's reported missing until Castle locates his body.
- Busman's Holiday: Castle's flying to London with Alexis for a mystery writer retreat at 221B Baker Street when someone murders the Air Marshall on the flight.
- Chandler's Law: The second that Castle and Alexis deduce which flight attendant was responsible for Ford's death, she re-enters the first-class cabin, pointing Ford's gun at them. Fortunately, Alexis is able to talk her down.
- Chekhov's Gunman: The episode has some more screentime than usual for one particular man asleep in his seat. It turns out he's been drugged by the murderer, for the MacGuffin he was wearing on his person.
- Closest Thing We Got: With Air Marshal Kyle Ford missing/dead, crime novelist and P.I. Richard Castle is the closest thing to law enforcement on Oceanic Flight 57. The pressure to find and apprehend the killer is compounded by the 300 passengers and crew on board the flight, his daughter among them.Castle: Which in itself is cause for concern.
- Death in the Clouds: The premise of this episode.
- Even Bad Men Love Their Mamas: Zig-Zagged and ultimately averted. Haddad is an exchange student on the no-fly list because his cousin joined ISIS. His getting on this plane with a stolen passport was only because he desires to be with his mother in her final days; he had no part in Ford's murder. Once the murder is solved, Castle ensures that before serving time, Haddad can see his mother.
- Freudian Excuse: Having her retirement robbed from her because of the company she worked for restructuring, and still having to serve the auction house apprentice who brags about the "money strapped to his wrist" every month, drove Debbie the flight attendant to try and steal the man's current "shipment".
- The Heist: One-person example. The real killer's motive was to steal an incredibly valuable watch under Ford's... uh, watch. When Ford saw that Rich had fallen asleep, he realized what had happened, then tracked the culprit down to the cargo hold, where she struck him dead out of desperation.
- Inside Job: Castle and Alexis realize that the culprit has been able to do things and possess knowledge that only someone working for the airline could have access to. Namely, one of the flight attendants.
- MacGuffin: Introduced late in the episode is the object that the killer was trying to obtain: a $13.3 million dollar timepiece, held by auction house apprentice Aaron Rich (the guy who's asleep in his seat for most of the episode) and secured by Kyle Ford. The killer had succeeded in swapping the Celestialis with a fake, but to do so, Rich had to be drugged asleep—and once Ford saw Rich asleep, he went after the culprit in the cargo hold.
- Noodle Incident: During the video call, Beckett lets an on-edge Castle know that "the racecar driver did it".
- Red Herring: The turbulence at the beginning of the episode has nothing whatsoever to do with the events, nor was there any terrorist threat.
- Screams Like a Little Girl: Castle lets one out when he first sees a (secured) snake in the cargo hold.
- A Sinister Clue: Alexis and Lanie deduce that Kyle Ford was taken by surprise by a left-handed attacker, judging by the angle of the wound to his head.
