风吹草动

fēngchuī-cǎodòng

[the slightest sign of disturbance; at the mere rustle of leaves in the wind; be sensitive to the slightest upset as the grass bends whenever the wind blows] 有风吹, 草就动。 喻指因轻微的动作而发生影响

万一有些风吹草动, 不要我管门起来, 赶得出去, 就是个死。 --《二刻拍案惊奇》