play into sb's hands 正中下怀；干敌人（或对手等）所希望的事；授人以可乘之机；中计；做出有利于某人的举动

【例句】
Your agreeing to take the business trip in another city well played into the hands of the boss. As for the reason, you put it in the pipe and smoke it.
你同意到外地出差正中老板下怀，至于原因，还是留给你自己去思考吧。

If we get the police involved, we'll be playing right into the protesters’ hands.  
如果出动警察，那将正中抗议者的下怀。