在这部气体人第一号犯罪/剧情/爱情片中,連続強盗殺人が起こるが、現場は完璧な密室。手掛かりをたどると春日流舞踊の家元・藤千代の家にたどり着く。平凡に暮らしていた水野は人体実験のために異形の人となり、落ちぶれた藤千代のために悲しき犯罪を重ねるのであった…。東宝の特撮技術と本多猪四郎の演出による重厚な人間ドラマが融合し、「変身人間シリーズ」の中でも最高傑作の呼び声も高い１本。
A librarian is subject to a scientific experiment which goes wrong and transforms him into 'The Human Vapour'. He uses his new ability to rob banks to fund the career of his girlfriend, a beautiful dancer. The Human Vapour is ruthless in his quest for money and kills anyone who stands in his way, especially police. He soon becomes Tokyo's most wanted criminal. Can he be stopped before he kills again?
