Tooru Amuro or Rey Furuya is the Black Organization member nicknamed Bourbon. He actually something like secret police agent (I can't remember the organization's name) who is working undercover in BO. He as Tooru Amuro works at Poirot Cafe, and become Kogoro's apprentice.
I remember a case when Amuro, Conan, Ran and Kogoro are at the hospital and there's a case where a posion is used in a tea.
After Amuro and Conan realise who the suspect of the cases is, there's a kid with her mother counting the lift that coming from the upper floors. When the kid counts to zero (they are on the ground floor), Amuro hears that and he seems surprised about it. He also has a flashback to when he was a kid and was called "zero" by a woman.
So, who is she? Who's the woman who speaks to with young Amuro? What is their relation? And also why he called "zero" by this woman?