Holmes is bored, so he drags Watson out to the site of a plane crash. And he immediately spots that one of the victims was actually dead before the crash, so there's a murder to investigate! They start by working on the passengers (a bunch of lawyers who fought a lot), but Holmes eventually determines that the victim was probably dead before the plane even took off. So the other two passengers didn't even know he was on board! Well, in the cargo bay.
Meanwhile, Watson has a dinner appointment with Holmes's father. Holmes is also invited, but he doesn't believe his father will actually show up. And he's right! But Watson doesn't find that out until after she has a conversation with an actor Holmes hired to prank her. This makes her mad until she discovers that the actor is actually a friend of Holmes's.
The investigation continues with the other employees of the company that owned the plane that crashed. One of them was smuggling cocaine from Miami! Well, I guess technically the smuggling happened right before the cocaine got into Miami, but he transported it up to New York. And the other employee assures Holmes and the police that that guy totally did it. But he does such a bad frame job that even Bell is like, "This is a terrible frame job." In order to get him to confess, Holmes has to show off his deductive skills and prove that he's got a giant wound somewhere that's being held together with airplane glue.
Watson misses that last part, because she goes off to have another conversation with the actor from before. The actor takes awhile to say anything useful, but Watson eventually learns that Holmes feels very strongly about a name that he was repeating while stoned out of his gourd nine months ago.
The name: Irene.
Watson awakes to a cacophonous noise. It's Holmes's police scanner, which he left set on "incredibly loud" while he went into another room for cereal. He's been listening to the scanner for days because Gregson hasn't called him for a regular case. Also, he's using a real radio scanner instead of just using a website like a normal person. Watson says Holmes's father is coming to town and would like to have dinner. Holmes points out that she's never met him and has only contacted him electronically. He assures her that his father has zero intention of seeing them because his father never follows through on things. I immediately jump to the conclusion that Holmes hired her himself through a byzantine series of stand-ins. Then something comes on the scanner: a code 1066, which is an "unusual incident": Holmes has narrowed it down to a plane crash. And they're off!
They find Detective Gregson at the plane crash. Holmes wants to help, even though it's not a crime scene. Even Gregson is only here to push away the onlookers, according to the actual person in charge. She's Miss Molinari, if you're curious. And why wouldn't you be? I can't just call her "Plane Investigation Lady" all the time. Holmes noses in and asks Miss Molinari some questions about the crash. He claims to be "an expert in the field of deductive reasoning and unraveling the complex chain of events that can turn a triumph of human innovation into a smoldering pile of wreckage in seconds." That's an awfully specific field. Miss Molinari politely declines his help, and Gregson offers to give Holmes some Cold Case Files to keep him occupied. Holmes walks into the scene and starts looking at things. There are dead people among the wreckage.
Holmes establishes that all three of the passengers were attorneys. One man's leg was nearly cut off by the fuselage, but there's not much bleeding on his clothes. Holmes concludes, "Someone caved his skull in before the plane hit the ground." So he was murdered before the plane crash.
After the commercial, Holmes has an audience as he describes the murder weapon: a large wrench. The flight recorder hasn't been recovered, but there was a witness to the crash. Everyone speculates about who could have killed the passenger. The pilot? One of the other passengers? Holmes finds some sand that's not natural, but he figures it was probably trucked in to offset erosion. Watson thinks the murderer must have died in the crash, so she doesn't know why Holmes is so intent on solving the mystery. Well...because he's obsessed with solving mysteries? Holmes explains that there's a story that needs to be told, and she accuses him of just trying to avoid his father. Holmes wants to talk to the last people to see the passengers alive.