In the dead of night, a man is found dead of carbon monoxide poisoning in his shower. Forensics’ careful investigation reveals that the killer came in through the air vent, with the footprints revealing it to be a man. But the deceased’s mouth and nose show signs of pressure, with these signs containing traces of rose essence. Coincidentally, his wife runs an aromatherapy parlor, but she was working late that night, and has a strong alibi. Investigation finds that her ex-husband also died in a carbon monoxide accident. Is this a murder or accidental? Could the wife who was nowhere near the scene of the crime really be the murderer?