where there's smoke there's fire直译有烟的地方必有火 ，引申为无风不起浪。

【例句】
She must have done that sort of thing. Where there's smoke there's fire.
无风不起浪，我想她肯定做过那种事。

Well, that's what they said, but there's no smoke without fire.
当然，那是他们说的，不过无风不起浪么。