Word was just passed to the Tokyo Police Department that a local bank has been robbed. Detective Shinichi and Officers Takagi and Takagi have been sent to the scene. Detective Shinichi believes the thief hasn't gone far, and decides to search the area. They search Mitsuhiko's Laundromat, however are unsuccessful. They then search Genta's Grill, a diner, but once again, find nothing. The next closest building is Mika's Digital Photos. They go inside, talk to the owner, and are able to look around. After finding nothing, they come across a small closet in the back of the building. When Detective Shinichi asks to look inside, the owner says, "I would, but that is my darkroom, where the pictures develop. If you open the door and let light in, it will ruin all the pictures." Detective responds, "Okay, but we'll now have to arrest you. You are the bank robber, and the money is hidden in this building."
Where is the money, and how did Detective Shinichi know?