Couldn't pass up a murder mystery game. The search mechanic is a good premise! If you continue building on this idea, adding some danger or a time limit (or both) could increase tension in a good way. Also, having the clues you find be small pieces of stories with random names, places, etc. could make the game feel more story-driven.
Unrelated: I accidentally figured out how to clip through one of the windows and skipped two of the keys. Just haven't figured out how to skip the blue key yet. :) Surprise alternate gameplay mode, haha