Question

به کاهدون زدی (اصطلاح بفرمایید)

Answer 1

You're robbing an empty bank. (It's made up, not an authentic one)

Comments

Good imagination, (+1)

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Tnx for your generosity

Answer 2

end in smoke.

 The robbers excitement ended in smoke the moment they learnt that the robbed oldman was mere a pauper.

 

http://www.usingenglish.com/reference/idioms/end+in+smoke.html