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A wilted flower in Joan Whiting's (Joan Barclay) lapel reveals the presence of the invisible gas and Martin Andrews (Herman Brix) and his friends are able to get out of the laboratory in time. Following an old Chinese proverb, Andrews deduces that Victor Poten (Bela Lugosi) is holed up in Sonya Rokoff's (Luana Walters) apartment. But Poten and henchman Healy (William Buchanan) manage to escape over the rooftops, however, and Martin faces a furious but still zombified Grogan (Charles King). As chapter 13 concludes two bodies are seen hurtling from the roof.