Private Eye Diesel is a new episode.
Diesel pretends to be a private eye detective to solve a mystery involving Ben going missing with Thomas being his trusty sidekick.
The episode kicks off with Deadpool doing his theme song and says that Madame Transformersprimefan finally stopped playing Pokemon Go! to create this episode. She tells him to be quiet and stick to the script. RedSilver56 tells him that isn't even what happened. Deadpool tells them both to shut up and let him tell the story.
In the actual episode, Diesel is chugging down the tracks, pulling some mail cars to the Diesel Works. "Mail's here!" he calls out. The Diesels take a break while Mavis helps Diesel hand out the mail. Diesel pulls out the Muramasa Blade, which he then says he believes it belongs to Deadpool. The Merc snatches it and polishes it. Arry and Bert try to hold back their laughter at this. Thomas rolls in and tells them that Ben has gone missing. Diesel 10 is shocked and asks what happened. Thomas explains that Ben was going to see Hiro for advice on something, but he never arrived. Then Deadpool makes the Diesels talk very softly, where only their voices are heard and not what they are saying. He talks to the audience, saying how this is the origin story of a detective begins. RedSilver56 tells him that he wouldn't know that, since he never reads mystery novels. Deadpool doesn't listen however and continues.
Back with the Diesels, Diesel says that he'll solve the mystery and find Ben. Diesel 10 breaks out his old detective parts from his childhood and lets Diesel use them. Diesel puts them on and starts calling himself Private Eye Diesel. Deadpool says he likes it, and talks to the audience before RedSilver56 shoots him with a shotgun. Back with the Diesels, Diesel asks Thomas to be his trusty sidekick. Thomas pulls out his old Watson costume and puts it on. Diesel laughs and says that this case is definitely going to be a funny one. Deadpool replies by saying, "Elementary, my dear Watson!" Diesel 10 loads him into the cannon and fires him into the ocean. The Diesels and Thomas laugh when he gets eaten by a shark, who happens to be Jaws. D10 gives the shark a 100. Then, Nighlock, who is wearing his Bob Tanansky disguise, shows up and gives them a file on the case so far. They discover the last person to have seen him was the Fox named Nick Wilde, who sometimes takes time off to sell pawpsicles. The two go to find Nick, who is just coming out of the movie theater. They learn from him that another last person to see him was Yak. They learn from him that Ben met with Mr. Manchas to give Mr. Big his regards for not being able to attend the family reunion. They go to see Mr. Big, who reveals he invited Ben to the family reunion, but Ben never showed up, since he had to take care of something else that day. Deadpool talks to the audience, saying that so far, Ben was invited to a family reunion by a crime lord, and he never showed up, because he had something else to do, but what? Mr. Big takes notice of this and asks the two if someone's taken him to a hospital yet. Thomas admits that everyone has tried. Mr. Big suggests they talk to Manchas. They go over to the Rainforest District, where Manchas is watching his favorite TV Racing Show. He explains that Ben told him that he wouldn't be able to attend the reunion, because he had somewhere important to be, and that he wasn't really going to Hiro's in the first place. Manchas explains that Ben wouldn't tell him where he really was going, because he said it was a secret.
Confused, they thank him and leave. They