The episode starts with a recap of the previous episode, where Richard, Rachel, Conan, and Harley come home with Mrs. Tarrington to find her husband Rudy dead. While Conan is laying sick in bed in another room, Harley has just announced that he knows who the killer is. Inspector Meguire and Richard are both very curious as to who it is, but Harley tells them to be patient. Harley is dissapointed that Jimmy Kudo hasn't shown up to solve the case first and decides that he was wrong about him being a great detective. He then recounts that the murder would have only taken 5 to 6 minutes, meaning that whoever did it wouldn't have been rushed. He then tells them that the butler, Franklin Keene, and the wife, Camiel Tarrington, are both cleared because they weren't in the house at the time. He then says that Thomas Tarrington and his fiancee Jasmine were both upstairs, but they didn't have enough time to commit the crime before Harley and the rest arrived. Harley then acusses Rudy's father, Theodore Tarrington, of doing it. He reveals that he found fishing wire in the trashbasket in the room Theodore was waiting in after they arrived. Harley remembers that when they first arrived, they met Theodore coming down the stairs seeming a bit flustered. He then went downstairs and poorly hid the wire he had used for the sealed room trick in the trash. Theodore looks shocked but admits that Harley is correct, he is the one who killed his son.
Meanwhile the doctor arrives, and Rachel ushers the doctor up to Conan's room. She is shocked when they find Conan missing. She searches frantically for him, but all that remains in the room is Conan's discarded red bowtie. She asks the officers standing outside Rudy's study if they have seen the boy, but no one has seen him. Suddenly Jimmy Kudo himself, in his 17 year old body, enters the room and tells everyone that Harley is wrong, that's not how the murder happened. Everyone is schocked at Jimmy's sudden appearance and Rachel breaks out in tears at the sight of him. She demands to know where he has been, saying that she was worried about him. Jimmy asks why she is crying, but she denies it. Harley, upset that his theory has been criticized, says that Jimmy is just mad that he cracked the case first. Jimmy, out of breath, tells Rachel to hold tight for now, this won't take long. He then tells the room that Harley's explanation, while entertaining, is entirely impossible. Meguire protests, saying that Harley had done a demonstration of the sealed room trick on him and it had worked perfectly. Jimmy asks Meguire if the key is really in his inner pocket, as it was found in Rudy's. Meguire finds the key in his outer pocket and Jimmy explains that when sitting, the pathway through the pocket becomes restricted, causing the wire to snap loose while the key is in the outer pocket. Harley says that it could still work, but Jimmy points out that Rudy's key was found neatly folder inside the inner pocket, which would be impossible to do with wire. Jimmy explains that wire has been planted all over the house to make sure Theodore would be a suspect no matter where he went after going downstairs. Harley says that Theodore even confessed, but Jimmy says that he didn't do it, he was just trying to protect his son's real killer.
Harley protests that the only other possibility would be suicide, but Jimmy reminds them that there was loud opera music playing and several books stacked in front of Rudy when they had first entered. Jimmy tells them that what really happened was much more disturbing. He explains that the books were placed to hide Rudy's pained expression as he died, and the music was turned on to cover any sounds he might have made. Harley asks who the murderer was trying to hide these signs from, and Jimmy says from whoever entered the study. He asks who first approached Rudy when they entered earlier and says that the murderer was you, pointing at Camiel. The butler asks her why she did it, and Jimmy explains that she killed Rudy right in front of them. She had given him sleeping pills earlier before she left for the Moore's, then while she pretended to wake him up when they returned, she stabbed him with the poisoned needle. No one had a clue what she was doing and Rudy died instantly. Jimmy then says that even if an autopsy revealed the sleeping pills, it would be blamed on whoever killed Rudy. Harley tells Jimmy that the theory is ridiculous because Camiel had no needle in her hand when she went to awaken Rudy, but Jimmy points out that her keyholder had the same design as Rudy's, so it also opens up. Meguire tells her to open it and there is a small indention cut that is the length and width of the poisoned needle used to kill Rudy. Jimmy predicts that they will find traces of Ricin, a potent poison made from the castor bean plant, on the keychain. Meguire asks why Camiel would have done it, and Jimmy points out a photograph nearby of Camiel and Rudy in their youth. Everyone is shocked as they realize that Camiel looked just like Jasmine when she was younger. Camiel admits that Jasmine is really her daughter from her first marriage. She explains that her first husband, Senator Mori Yasmeen, was forced out of office by Rudy to avoid an indictment over bribery. Rudy framed Mori into being put into prison, where the senator died. Rudy had wanted Camiel for himself, so he got rid of Mori without Camiel knowing what had happened. At the time Camiel had a breakdown and was briefly institutionalized, leading to Jasmine being adopted by Camiel's sister.
Camiel explains that when Rudy saw Jasmine dating his son Thomas, he became furious and basically admitted to getting rid of Mori, leading Camiel to come up with a plot to kill him. She framed Theodore for the crime because he was in on Rudy's plots back then. Theodore tells them that he was a different man back then and he confessed in an attempt to help repent for his wrongdoings. As Camiel is led away she tells Thomas to make her daughter happy and not turn out like his father did. Harley theorizes that Camiel came to them in the first place pretending to distrust Jasmine so that no one would suspect that they were related.
After the police leave, Jimmy starts coughing hard. Harley asks where Jimmy was earlier and he replies that he got a tip from Conan that there was a new detective looking for him, so he wrapped up the case he was on and rushed over on a train. Rachel then acusses Jimmy of spying on her, but Jimmy just laughs. She tells him that it really hurts always worrying about him, and he replies that he is a detective and he is sorry that he isn't around, but that's how he is. He starts coughing hard again and Rachel goes to find the doctor. Harley watches Jimmy and tells him that he wouldn't have given Jimmy Gin and Vodka if he knew he had such a weak stomache. Jimmy tells Harley that he must always remember that one truth prevails. Harley tells him to remember those drink names and Kudo falls to his knees. Harley tells him to hang on, help is on the way. Jimmy's heart is pounding, he is cold, and his bones feel like they are melting. He knows that he is reverting again and knows that he can't let them see him change. He begins to rush off, but Rachel returns and tells him to stop. Jimmy turns around and falls backwards off the stairs so that she won't see him. Rachel rushes over and finds just Jimmy's clothes laying at the bottom of the stairs. She runs down just as she hears Jimmy scream. She tracks the noise to a closet and thrusts it open, only to find the missing Conan sitting inside. She asks him where he has been and Conan tells her that he got sweaty, so he borrowed some clothes from another room. He then tells her that Jimmy had another case and had to leave, but he asked Conan to make sure no one mentions his role in solving the case. Conan, totally exhausted, then passes out.
After 3 days of bedrest, Conan finally recovers. Harley went home and Jimmy's suprise appearance was left out of the papers, keeping his secret safe. Conan tries to figure out what made him suddenly revert and remembers that his pains started after drinking from Harley's bottle. Conan runs to get a glass of the liqour, but Rachel sees him and locks the bottle up where he can't get to it. She tells him that she puts up with Richard drinking, and she won't have him doing the same. Conan reflects that even though he is really in the 11th grade, he is still a minor. Rachel tells him to hurry up and get dressed because his friends are waiting outside for him. Conan goes out and finds Amy, Mitch, and George waiting on him. Amy tells him that they were worried about him, but George says he envies Conan for missing 3 days of school. They lead Conan to the library and explain that he has to make up a book report, so they are going to help him. Conan understands why Amy is excited to help, since she would have a root canal to be with him, but doesn't understand why the other two are acting so happy. He decides to play along, since if he gets ahold of the liquor again, he may never have a chance to play again. He figures that this won't last forever.