- Punishment detective Labra! This might be fun...
– Labra, to herself, trying to take matters in her own hands.
The episode is followed up by Defeat All the Ghosts!.
Labra enjoys snack time in a box. But when she opens the box, she is shock to find out that her snack has disappeared. When the gang comes for an inquiry, Airi says her snack must've disappeared before her break. In conclusion, anybody in the house could be the thief, so everyone decides to figure out who is the thief.
While Airi decides to take charge who the snack thief is, Ruby, Larimar, and Luna wants to be detectives too with her to find the thief. They all thought of magically changing into their human forms to use their magic to solve the mystery. But, they all distinctively point fingers at Labra, claiming to be the thief. As the four argue against each other who should be the detective, Labra is beginning to doubt they are of any use at all and is considering of taking matters into her own hands.
Airi settles down the topic of using magic and states they should solve the problem to themselves only. Airi begins to brainstorm, then comes up with a theory. She states that the room they are in has a locked window. And that the only way the thief can come in is through the door in the room. So she declares the thief could be any of the Jewelpets. However, they argued that Airi herself could be the thief. This leaves her started and the Jewelpets start getting ideas about her. Then they end up chasing her around the room.
Sakutarō comes into the room. Airi sees him and hides behind him pleading for help. Sakutarō wondered what was going on, but then the Jewelpet notices a food filling on his cheek, and Ruby distinguishes it as a Mont Blanc cake. Larimar ask where did the crumb came from. He stated it was a sample from a similar box in the same room. The Jewelpets then conclude that Sakutarō isn't the thief. Sakutarō also adds that he never knew it was Mont Blanc due to its unusual color he claims.
Larimar and Luna then asked how Ruby knows it was Mont Blanc, saying they never knew what a Mont Blanc looks like. It then leaves Ruby nervous and panicky. The Jewelpets then start to realize Ruby is the thief and Labra, out of anger, attacks Ruby.