Mouri is invited by a horoscope reader to meet for the publisher. She is later found dead in her room. Conan figures out the culprit by figuring out his simple plan.

Moore and the policemen have deducted the wrong conclusion that this room is not a locked case and that the criminal told the victim to lock the door and the victim died of poisoning. Conan proves them wrong stating how the coffee spill is weird and how the cake is cut in two but put together in one plate. Conan shows them it is indeed a locked room case and that the murderer is not with them. The case is solved with a sad conclusion, in the rainy day.