Setup: A poisoned collector is lying in the room. There’s a broken aquarium on the floor, and water has flooded the carpet. The cleaning lady, the son, and the gardener are suspects.
Solution: The killer is the cleaning lady. The water from the broken aquarium soaked into the carpet, but the cleaning lady’s mop and bucket in the corner are wet, with traces of aquarium algae. She tried to quickly wash away the traces of the spilled poison.
