Houtarou's mysterious sister showed up at the school's festival. She bought a copy of the Hyouka anthology and gave a manga to Houtarou, "A Corpse by Evening". This is the same manga that Mayaka was looking to show to her manga club mates. The festival continued. We saw more of Mayaka's depression and Satoshi's jealousy toward Houtarou. After reading part of "A Corpse by Evening", Houtarou was able to connect it to the thefts mystery.
Episode 16 of Hyouka was a delightful mixture of a bit of everything. I am perplexed by how Satoshi can be happy that Houtarou is good at solving mysteries but at the same hates it. However, I am glad to see that Mayaka seems to have recovered her positive energy with the apparition of "A Corpse by Evening". This episode gets a 9 out of 10.