On a plane headed for London, Castle and Alexis end up in the middle of a murder investigation at 30 thousand feet.

*****SPOILERS BELOW*****

Castle and Alexis are on a flight to London discussing their plans for father-daughter time to distract themselves from, what looks like, some of the worst turbulence I’ve ever seen, when the flight crew start acting sketchy.  Castle, being Castle, decides to go ask them what’s up.  The captain of the flight (Lisa Kaminir) tells them the air marshal, Kyle Ford (Brien Perry), sent a text to his supervisor about a security issue on the flight, and now Ford is missing.

Castle tells them he will help look for Ford and try to figure out what’s going on.  I mean they are 30k feet above ground, so I’m thinking he has to be somewhere on the plane.  One of the flight crew takes Castle into the baggage area to look for Ford, where Castle ends up finding Ford’s body stuffed into a large piece of luggage.  Excitement doesn’t leave Castle alone!

Castle calls to tell Beckett about the situation, and that the air marshal’s gun is missing as well.  Castle is getting Beckett on board to help him get the case solved before anyone gets hurt.  Alexis decides to help with solving the case by putting the training she got with Lanie to good use and take a closer look at the body.  Some of the flight crew remembers seeing Ford near the back of the plane, so Castle goes and talks to one of the couples, who he thinks may have gotten video on their phone, to try to figure out what he was doing.

Alexis calls Lanie on video chat so she can look at the wounds.  Lanie says there were no signs of a struggle and it looks like the person who did this was left-handed.  A video from the couple’s phone shows that Ford was watching someone at the back of the plane.  The person in that seat is supposed to be an “Isadore Baldon,” but Beckett says after checking it out that the man in that seat isn’t Baldon, and that Baldon’s passport was stolen nearly a week ago – so the man in that seat could be anyone.

The flight crew wants to take the mystery man into custody, but Castle says if he isn’t their killer then that could alert the killer and possibly cause him to get even more hostile.  They get mystery man’s cup and test it for fingerprints.  Alexis sends a picture of the fingerprint to Beckett who runs it, and it turns out their mystery man is Aiman Haddad (Nick Green).  He’s a Syrian national in the US on a Visa and 5the FBI has him on the “No fly” list because he is associated with ISIS.

Upon receiving this information, Castle and crew decide it’s time to detain Haddad.  Haddad catches them talking about this and makes a run for it.  He goes into the bathroom and makes a call, which one of the crew translates as him saying “They know and it will all be over soon.”  It isn’t looking good at this point for Castle and the passengers of this flight!  They can’t find the gun, so Beckett says Castle will need to interrogate him.  Haddad also has a checked bag on board, so they need to locate that to make sure things aren’t about to hit the fan with a bomb situation.

Alexis and one of the flight crew find Haddad’s bag and, of course, nothing in the bag speaks to terrorism.  It seems like Ford may have gotten some texts from a personal phone, so in one of the biggest twists ever, the guy with ISIS ties on a flight using a stolen passport, might actually be innocent.  They find the other phone and, creepily, use his lifeless hand to unlock the phone.  Turns out someone was texting Ford threatening to take down the plane.

The tech team discovers that the phone used to text Ford was purchased in the airport prior to takeoff by Marilyn Singer (Kincaid Walker), a former Oceanic Airlines exec who recently accused the airline of blackballing her.  Castle smoothly pours some wine on her in an attempt to “isolate” her, which leads to her going for her bag and uncovering the gun.  Marilyn claims this is all a setup and Ford is her boyfriend.  We got ourselves a good ol’ frame job on our hands!

Ford’s account shows a large transaction from Victor Dietrich (Roy Werner), a rich German businessman.  Dietrich denies knowing Ford and any involvement.  Once Dietrich finds out Ford is dead, he changes his tune and says Ford was providing security for an apprentice that was wearing a $13 million watch.  It turns out this wasn’t about terrorism at all, and it was a simple heist.  Whoever planned all this had insider access and was probably playing double agent with Castle and Alexis all along.

It turns out it was one of the flight crew, Debbie Parker (Paula Newsome), who was unhappy with Oceanic’s recent elimination of their pensions.  Yikes.  Poor lady.  That took an unexpected turn.  Moral of the story: be careful who you’re bragging around or it may lead to someone planning a con centered around you?

What did you think of the episode?  Comment below!

Castle airs on Mondays at 10/9c on ABC. Watch full episodes on ABC.Go.com, Hulu and Amazon Instant Video.