snake in the grass
見利忘義，背后搞鬼，暗中挑撥離間
口語·形容陰險小人
英文釋義
someone who appears friendly or harmless but is actually treacherous or deceitful
例句
Don't trust that guy; he's a real snake in the grass.
典故來源
源自《伊索寓言》，蛇藏在草叢中不易被發現，比喻暗中使壞、表面友善的人。