S01E273: Old Lady's Quiz Disappearance Case

The Detective Boys meet an old woman in the park who feeds and takes care of stray cats, and also likes to give the kids quizzes from a puzzle book she has. The next day she doesn't show up to feed the cats, but the cat Bruce comes with the old lady's scarf around his neck. The scarf has a code and blood on it, and to find and save the lady Conan and the gang must solve the puzzle.