a wolf in sheep's clothing
书面/口语·形容伪善者或隐藏的威胁
例句
He seemed so kind at first, but later we realized he was a wolf in sheep's clothing.
典故来源
源自《伊索寓言》中狼披上羊皮混入羊群的故事，比喻伪装成善意的危险人物。