Wait, the user might want specific details about the episode. If I'm unsure about the exact plot points, I can mention general aspects common in the Sherlock Holmes arc episodes. For example, the students being trapped in a room, a mystery involving Holmesian elements, and Conan using his wits to solve it.
In the Sherlock Holmes arc, Conan and the students play roles as various Holmes characters. Each case is a reenactment or parody of a Holmes story. So episode 487 might be part of this arc. The main conflict is usually an unknown killer among them, with Conan deducing the culprit. The culprit is often the host or someone with a motive. detective conan episode 487
I might need to mention that the episode is part of a larger arc, so context is important. Also, note any cultural differences or how the creators adapted Holmes' stories into the anime. Wait, the user might want specific details about the episode