The episode begins when Finn and Jake in the Candy Castle. They are playing with cats in suits, with Princess Bubblegum following them, and go into one of the rooms of the palace. They are suddenly interrupted by Lumpy Space Princess, who claims she was robbed and that the thief stole something she cannot live without. After Finn and Jake try to calm her down, Princess Bubblegum enters the room with an abnormally large syringe filled with green liquid. Princess Bubblegum then injects Lumpy Space Princess with the liquid, which is revealed to work as a tranquilizer. Finn asks her who robbed her, but Lumpy Space Princess only manages to utter what sounds like "Pete Sa—" before fainting. Finn and Jake then search Lumpy Space Princess for clues, but all they find is a key to room 303 in the Coolest Hotel.
When the two arrive at room 303, they bust down the door and quickly investigate. They find only bags. Finn then notices a drug store across the street. He also finds what appears to be blood on the floor and asks BMO to find out whose it is. Finn guesses the murderer must have bought a mini adhesive bandage afterwards, so Jake turns into a car and the two burst through the window. In the Candy Drugstore, Ann is suspiciously selling bandages to a candy person. Finn introduces himself and Jake, who shapeshifts into a police badge and asks if anyone suspicious bought bandages today. She says she cannot remember all the customers. Finn starts to leave, but Ann then tells them about this person who had a nosebleed. She says his name was Pete Sassafras and that he is catching an 11:27 train at platform five in the Candy Kingdom Station. Finn and Jake leave to find Pete.
At the train station, they find platform five and look for suspicious people. They see a "nasty tranch" wearing a "skeezy" trench coat about to board the train. They go after him only to be stopped by Blueberry Cops, who try to arrest them for boarding the train without a ticket. Jake explains what they are doing. The cop holding Jake licks him and says he tastes like police, so they let them off the hook. Jake turns into a car once more and swallows up Finn so he can drive. They take a shortcut through the woods to catch up with the train, crashing into trees, deer, and even going through a river along the way, but they catch up. The two enter the back of the train and find Pete, acting suspicious as they question him. Jake then turns into handcuffs, and they arrest Pete.
In the Candy Dungeon, Finn and Jake are standing near the captured Pete. He claims he does not know anything. They ask him a few questions, but all they discover is that Pete does not even know who Lumpy Space Princess is. Pete demands a lawyer, so Jake stretches his arm into one. Pete is pleased until Finn and Jake laugh, revealing the joke. After some time, the two leave to get some donuts.
Outside, Finn tosses Jake, who is in the form of a car, a bag of donuts with a cup of coffee inside. They talk about the case and think about becoming professional detectives when BMO finds them and tells them about the blood. It says it found out it was not blood, but tomato sauce, and then Finn begins to piece together the puzzle. He deduces that Lumpy Space Princess was not saying "Pete Sassafras," but actually "Pizza Sassy's," a pizza parlor. Finn and Jake rush to the parlor and ask an employee for the pizza delivery guy (called Pete), but they are told that Pete is out delivering pizzas. They think LSP is in danger, so Finn calls Princess Bubblegum to tell her to add Banana Guards outside Lumpy Space Princess's hospital, but she tells him that Lumpy Space Princess has gone back to her hotel room. Finn and Jake hurry to the hotel, panicking when they see Pete's pizza delivery car parked out front.
Hurrying to Lumpy Space Princess's room, they hear Lumpy Space Princess grunting and shouting. Jake kicks the door open and sees Lumpy Space Princess on top of Pete. Pete asks for help and tells them that he "was just delivering the pizzas she ordered, and now she won't let [him] leave." Finn asks Lumpy Space Princess what is going on. She tells him that Pete stole her heart and starts to sob. Finn and Jake remove Pete from under Lumpy Space Princess, but Pete complains afterwards because he did not get a tip. The episode ends with Jake transforming into a car and telling Finn that "the only case here is just another case of LSP being nutty," as Finn and Jake smash the window of her hotel room again.
- Candy People
- When Ann is getting the empty jar down, on the far right of the screen, there is a bottle with Norse runes on the label; they possibly spell out "Eelaei." Norse runes are also on the yellow carton next where the jar was sitting; they possibly spell out "Apreil."
- In the Candy Drugstore behind Ann there is katakana (Japanese) on the glass that reads ?, meaning "pharmacy."
- The station looks busier and more complex than it had been on "Mystery Train."
- This episode is a tribute to crime dramas such as Law & Order and The Wire.
- The transition from the drug store to the train station and in the previews of the episode had the noise similar to when a scene transitions on Law & Order.
- The train station appears to be loosely based on Grand Central Terminal, a location frequently used in Law & Order.
- When the cats are in the suits with a suitcase, this is similar to the character, Business Cat, from Cartoon Hangover's YouTube show, Our New Electrical Morals.
- Jake turns into a pipe that Finn inserts into his mouth. This is a reference to Sherlock Holmes.
- Finn and Jake buying donuts and coffee are reminiscent of the cops and donuts stereotype.
- The car that Jake transforms into is a 1980 Isuzu Gemini Coupe. The steering wheel is mounted on the right side, which is common in most Australian/Japanese cars.
- The cats Finn and Jake are playing with in the exposition resemble Box Prince, who is a cat from a later episode.
- Several connections to "Mystery Train" appear in this episode, including the return of the Candy Kingdom's train system (and many of the former passengers) and Jake transforming into a person (such as he did as "The Conductor").
- In the scene where Finn and Jake are arrested for trespassing in the subway station, a Gingerbread person resembling Gingerbread Rebecca can be seen on the top left of where Jake is, which was first found in "Fionna and Cake."
- Pete Sassafras reads a copy of "The Ooo Review" newspaper while on the train, which is first seen being read by Finn in "Slow Love".
- The Candy Kingdom's prison seen in "What Have You Done?" is visited again.
- On the train, Pete Sassafras has 4 fingers, but when he is in the candy dungeon he has 5 fingers, and then back to 4 fingers later.
- Part of the newspaper Pete Sassafras is reading on the train is miscolored in one shot.
- When Finn calls Princess Bubblegum on the phone at Pizza Sassy's, he makes noises that sound like he is inputting a number on a touch-tone phone. However, the telephone he uses is a rotary dial telephone, and would not have had any buttons to press, had he actually chosen to do so, instead of just making the noises. Oddly enough, his call is successful, despite not having actually dialed a number.
- When Finn and Jake return to LSP's Hotel Room, the door can be seen reassembled and tapped together, but when Jake turns into the 1980 Isuzu Gemini Coupe to crash through the window (again), the window appears perfectly intact. (Maybe it was completely replaced).
- This episode was originally going to be called "LSP Gets Robbed."