lone wolf

1. 不與人來往的人
   Nobody knows for certain what kind of man he is -- he's rather a lone wolf.

   誰也不知道他是什麼樣的一個人，他總愛獨來獨往。

wolf in sheep's clothing

1. 披著羊皮的狼
   We're dealing with a wolf in sheep's clothing.

   我們是在跟一隻披著羊皮的狼打交道。

cry wolf

1. 發假警報
   Nobody will believe he is in trouble because he has cried wolf so many times.

   沒人會相信他陷入困境，因為這種話他說過很多次了。

• cry wolf
  raise repeated false alarms, so that a real cry for help is ignored. [with allusion to the fable of the shepherd boy who deluded people with false cries of ‘Wolf!’]
• hold (or have) a wolf by the ears
  be in a precarious position.
• keep the wolf from the door
  have enough money to avert hunger or destitution.
• throw someone to the wolves
  sacrifice someone so as to avert trouble for oneself.
• a wolf in sheep's clothing
  a person who appears friendly but is really hostile. [with biblical allusion to Matt. 7:15.]