Episode 942: Find Maria-chan! (Part Two)
Scenario: Conan assists Detective boys over the phone to complete the treasure hunt to find Maria. Meanwhile, Yusaku Kudo and Hattori Heiji deal with the rumors regarding Shinichi.
The Detective Boys finally arrive to a bathroom but the only arrow points to the shower with nothing inside it. They convince Haibara to ask for Conan's help, and the latter tells them to give some water to the drinking bird next to the arrow. The Detective Boys give the drinking bird a glass of water and the bird starts to constantly dip its beak into it. They then notice the glass's water has reversed the arrow's direction, which now points towards the opposite direction of the bathroom. Another room which the kids fail to open. Wakita rings the doorbell at Professor Agasa's door and asks what the fuss in front of their neighbours' house is all about since he can't do his deliveries.
Conan tells the Detective Boys that the door isn't locked but the difference in temperatures between the cold corridor and the warm room where Maria is, creates a pressure gradient that can be dispelled by pushing the door strongly and opening a vent. Maria is indeed inside, asleep. She had come to watch some videos of her grandparents, but was then unable to open the door to leave the room, and concluded that she had to watch every video for the door to open.
As the room was accidentally airtight, Maria likely fell asleep due to heightened carbon dioxyde from her own breathing, which would have worsened if the Detective Boys hadn't found her in time.