Crystal-Clear Sleuthing! (Japanese: アローラ探偵ロトム！消えたクリスタルの謎！！Alola Detective Rotom! The Mystery of the Missing Crystal!!) is the 17th episode of the Sun & Moon series, and the 956th episode of the Pokémon anime. It first aired in Japan on March 9, 2017 and in the United States on July 1, 2017, as part of a three-hour special.
Professor Kukui and Rotom Dex are big fans of the TV show Alolan Detective Laki, and Rotom even has a blond wig so it can pretend to be the star. When Ash’s Electrium Z goes missing, Rotom excitedly takes the case!
Through video replay, Rotom tracks the Z-Crystal’s last known whereabouts to the schoolyard, where Ash and Kiawe were training. Rotom suspects Kiawe ended up with the crystal, but Lillie has another explanation: the video shows Ash putting it in his pocket. Ash remembers that he put the crystal on his nightstand before going to bed—and Pikachu triumphantly finds the missing Electrium Z caught in Rotom’s wig!
One night, Professor Kukui, Rotom, and Ash, along with Pikachu, Rockruff, and Rowlet, are watching a TV program called "Alolan Detective Laki". Laki is about to reveal the culprit of the case where the culprit made Mr. Makani hide his treasure which is the Princess Tear. Mr. Makani was coerced before disappearing as instructed. Rotom is a big fan of Laki and is wearing a wig similar to Laki's hair. Professor Kukui is also a fan of Laki and bought Rotom the wig. On TV, Laki reveals the culprit is the only person who knows where the Princess Tear is hidden but doesn't know he knows as well and reveals that the culprit is in fact the Doctor. When the Doctor demands to see proof, Laki obliges. Laki reveals that the Doctor has prepared a Sableye doll to replace the other in secret and reveals the Princess Tear which was kept hidden. Laki returns the Princess Tear to Mrs. Makani who is grateful but knows it will never bring her husband back.
Noticing that Ash has fallen asleep on the couch, Professor Kukui wakes him up and Ash goes to his bed. Rotom tries to tell him who the culprit was but a tired Ash tells it to tell him tomorrow before pointing out that Rotom is still wearing the wig. Rotom takes the wig off, putting it on the desk and goes to reveal who the culprit was only to find Ash is fast asleep. The next morning at school, Ash is panicking as he can't find his Electrium Z as he searches desperately for it and explains to the others what is wrong. Ash worries that Tapu Koko is going to be so mad and Sophocles mentions that Kiawe will be as well. Ash imagines Kiawe finding out that he lost the Electrium Z and using Inferno Overdrive on him as punishment. Rotom, wearing its Laki wig promises to get Ash's Electrium Z back. Kiawe arrives at school causing the others to panic as Kiawe wonders if he missed something as Rotom and Pikachu leave.
Searching the school, Rotom and Pikachu go into the staff room and inform Professor Kukui of what has happened. Professor Kukui remembers that yesterday, he spotted Ash and Kiawe working on their Z-Moves though as Ash was practicing with Rowlet, so he must have been using his Normalium Z. Believing that Ash may have dropped it in the schoolyard, Rotom goes to search for it. Standing above the school by the bell, Rotom looks through binoculars over the schoolyard but notices it is too big to find something small so asks Komala but Komala remains asleep. Using a magnifying glass, Rotom examines the ground around the schoolyard as Pikachu detects something in the ground and starts to dig only for an AlolanDiglett to pop up out of the ground. In the principal's office, Samson Oak is looking at a picture of him on the board when Rotom enters, asking what those pictures are of. Samson Oak explains that a cameraman from Alola TV came by yesterday and took them with plans to use them for next year's Pokémon Pancake Race poster.
Samson Oak mentions that the cameraman thought it was so funny that he shot a video by himself. Rotom learns that the cameraman recorded many events around the school and was impressed to see Ash and Kiawe practicing. This gives Rotom an idea and leaves with Pikachu to go to the TV station. Back in class, Professor Kukui informs the class that their next lesson will be dealing with Pokémon moves and to meet up in the schoolyard. They all head out but as Ash goes outside, Kiawe asks where Pikachu is. Ash makes up an excuse about Pikachu having leaving Kiawe disappointed as he was hoping to practice being hit by Gigavolt Havoc. Ash says that he wanted to train with Rockruff today. Kiawe becomes suspicious and wonders what is going on with them. Rotom and Pikachu arrive at the TV station where a security guard stands outside. Rotom manages to go inside but the security guard stops Pikachu from going in, finding him cute.
Inside, Rotom notices that Pikachu isn't with it. Rotom speaks to a cleaning lady who points towards a nearby cameraman who had shot the footage. Rotom goes over to the cameraman and asks to see the video he recorded. The cameraman explains the footage hasn't be edited but is in a hurry to get to his next assignment but Rotom promises to be quick as it only needs to interface with his camera for a small period of time. The cameraman allows it to as long as its quick as Rotom applies its hand to the camera and employs the Pokédex function for the first time and downloads a copy of the video. Back at school, Ash has Rockruff sniff his Z-Ring to try and get the scent of his Electrium Z, Kiawe notices what Ash is doing as Ash tries to get Rockruff to find his Electrium Z. Kiawe asks what Ash is doing as it doesn't look like he is training with Rockruff, Ash hurriedly comes up an excuse which Kiawe doesn't believe. Lillie quickly comes up with an excuse but Kiawe isn't convinced.
Rotom and Pikachu arrive back, Ash quickly asks them if they found out anything about his lost Electrium Z. Kiawe becomes furious and starts chasing Ash around the schoolyard. Rotom stops them and asks Pikachu gather everyone in the classroom. In the classroom, Rotom announces it has solved the mystery as Ash asks Rotom to stop keeping them in the dark. Rotom says it can't show him where the Electrium as it is still in the culprit's possession. Professor Kukui thinks Rotom is taking things a bit too far but Rotom reveals the culprit to be Kiawe. Rotom plays the video footage to show Kiawe and Ash shaking hands, explaining that this was the very moment that Ash gave Kiawe the Electrium Z. Kiawe says that it makes no sense as Lillie asks Rotom to play back the footage to where before they began training. Watching the footage, Ash is seen putting something into his pocket. Ash remembers that he puts his Electrium Z in his pocket after training and switched it with his Normalium Z.
Ash explains he had forgotten and remembers taking it out just as he was going to bed and placed it on the drawers. Pikachu pulls out the missing Electrium Z from the wig, everyone is shocked but Ash is pleased to have it back, Rotom realizes that when it put its wig on the desk, the Electrium Z got caught in the wig, which now makes Kiawe furious at Rotom, causing him to chase after Rotom as Sophocles notes that Rotom is on borrowed time. Later at Professor Kukui's house, Rotom is showing Kiawe, Ash and Professor Kukui video footage of Kiawe using a Z-Move, having edited it just for him. Ash finds it cool as Rotom says that if they ever want to record training, Rotom is capable of doing it.
Rotom updates itself with a video camera function.
When Rotom asks Komala where the Electrium Z is, its first seen with its mouth open, but in the very next shot, its mouth is closed.
On CITV's airing of the episode, during the part where Kiawe discovers Ash lost his Electrium Z, the scene where Kiawe lunges forward when he yells at Ash is cut, going from him looming over Ash to his face filling the screen. The scene with Ash dashing away when he admits to it is also slowed down.