A small provincial town near Paris, on New Year's Eve. Three childhood friends, including a postman, improvise an amateur burglary of their postal sorting center in a lighthearted mood to avenge their colleagues and friends who have been laid off in the name of unbridled liberalism. But the door closes behind them and the code changes. Trapped inside, they discover they are not alone. A young woman has locked herself in to find the breakup letter she regrets sending in the mail. At dawn, the door will reopen... onto a future in prison. From hope to disillusionment, from powerlessness to anger, the four friends frantically search for a solution that will get them out of this hellish trap.