The Crime
The police quickly came to the hotel room, they came to the emergency call of a woman who had been stabbed by her partner. They knocked down the door and found the woman dead in bed, the air conditioning duct was open.
The detective looked through the rectangular hole and noticed two lines that cleaned the dust and extended along the pipeline, the attacker had escaped crawling through the pipeline, then and surely he had to be in one of the adjoining rooms. When the detective arrived in the next room a man opened the door, he was wearing shorts and his knees were dusty, he had escaped crawling on bended knees.