 Conan and his caretakers, Ran Mori and Kogoro Mori, are given a free trip to London after finding a cat that belongs to Diana Kingstone, a rich British woman. For the trip, Conan is given two pills by Ai Haibara; the pills will temporarily suppress the poison which turned him into a child allowing him to use his teenage identity, Shinichi Kudo, to bypass airport security. After the medicine wears off, Conan rendezvous with Ran and Kogoro to visit the Sherlock Holmes museum. There, Ran phones Shinichi (Conan using his voice-changing bowtie) and is upset about his apathy. Shortly after, Conan overhears a child named Apollo Glass who is searching for Holmes. Posing as Holmes'apprentice, Conan befriends Apollo who reveals a man has given him a list of riddles which needs to be solved in return for sparing someone's life. Meanwhile, Ran meets Minerva Glass, a professional tennis player and Apollo's elder sister, who tells her to give up on love relating it to the tennis mantra "Love is Zero". Ran decides to call Shinichi; during the conversation, the latter accidentally reveals he is by Big Ben. Ran corners Conan forcing him to take the medicine for the return trip to protect his identity. Believing that Shinichi was hiding from her, Ran is hurt and repeats Minerva's words. In return Shinichi confesses his love for her and rebukes Minerva's statement by exclaiming that everything starts from zero.
