Conan received a call from Dr. Agasa, inviting them to join the "Izu Mystery Tours". It was actually for Agasa's friend and his granddaughter. But his granddaughter was ill, so Agasa asks Conan to take their place. Since Dr. Agasa said all the housing and eating are free, Mouri is pleased to go.

There are another seven persons besides them. Among them, is the sponsor, who will dress up like Night Baron and will cause some case in the hotel. Anyone who can appeal his identity will get free housing and eating. Since Dr. Agasa had confidence of Shinichi, he told him the trip was free. And Night Baron is a character in Shinichi's father's novel, who appears and disappears mysteriously in dark night, sometimes kills a person. Mouri, Ran and Conan meet the other people at the hall of the hotel. Conan can feel great murderous look among their sight.

Then, Conan stands at a balcony alone, thinking about the competitors' attitude, puzzled. "Is it really just a game?" Just then, Night Baron appears behind him. Conan is astonished at that scene. Night Baron pushes Conan down the balcony. Fortunately, Conan falls into the swimming poor down there, not wounded. When he runs back to the balcony, Night Baron has disappeared. Conan infers he must have changed his clothes in the toilet.

Conan telephones to Dr. Agasa, asking him about the trip. But Agasa doesn't know very clearly, too. He tells Conan, the winner will also get the secret program named "Night Baron". He doesn't know the content of the program. But the word "virus" is wide spread among they scientists these days.

During supper, Conan goes to their competitor's tables. He asks Gen'ichiro Kaneshiro, an old gentleman with a maidservant, about the virus. He says it is designed by a perfect engineer and nobody is able to find it out, so it can enter banks and cause crimes. The name of Night Baron comes from its appearing and disappearing mysteriously. Hearing the name "Night Baron" reminds him of his late son.

At the other table, Shiro Konno, a crazy computer fan, is listening to a call. In the call, Conan eavesdrops that Tokio Ebara, another member of the tour, is a hacker. When Conan turns to look for Ebara, he has left, forgetting to bring his tie. Conan accepts his tie preparing to give it back.

After supper, Ran and Conan return to their room. Out the room, Ran sees their neighbour, Satoru Maeda, he is forbidden to enter his room. For he had a bicker with his fiancee, Akiko Sayama. So he decides to avoid her for a while, inviting Ran to go with him to the roof. On the roof, Maeda praises Ran more beautiful than the night sky. Ran is a worshiper of Maeda, for he was the former championship of countrywide karate competition, and also for this reason, did Ran begin to learn karate. Ran asks him how he got to know with Akiko. He replies that they are childhood friends and he is also an intimate friend of her brother. But he died three years ago.

At the same time, Mouri is with Miss Hideko Kamijo, also one of the partners, at a pub drinking. He knows that she divorced three years ago. Hideko puts some sleeping pills in his glass.

Then Maeda decides to go back, Conan mentions the word virus. But it seems Maeda knows nothing about it.

At the end of this episode, when people relaxing at the square, Night Baron suddenly falls off the building, skewered on a bronze statue.