Cecil Disney, a noted chemist, is experimenting to discover how to manufacture artificial rubber. During one of his experiments he accidentally mixes two toxins, the combustion of which creates a deadly fume. In order not to be overcome by the lethal gas, he throws it in the laboratory sink and slams the hood down. At that moment, his wife, who was entertaining a friend on their cozy roof garden, left to go downstairs to procure a match for the friend’s cigar. The friend, who was seated near the standpipe that gave vent to the sink, inhales the chemical fumes. He is instantly killed. The chemist is arrested and about to be convicted for the murder, when the great detective, King, is put on the case and succeeds in solving the mystery.