a wolf in sheep's clothing
US /ə wʊlf ɪn ʃiːps ˈkloʊðɪŋ/
UK /ə wʊlf ɪn ʃiːps ˈkloʊðɪŋ/

1.
披著羊皮的狼
a person who appears friendly or harmless but is actually dangerous or malicious
:
•
Be careful of him; he's a wolf in sheep's clothing.
小心他;他是披著羊皮的狼。
•
The new manager seemed nice at first, but he turned out to be a wolf in sheep's clothing.
新經理一開始看起來很好,但他原來是披著羊皮的狼。