twelve o'clock
`` It is on the first floor , immediately facing the service staircase , and at the end of the long passage which leads to the main staircase . '' `` Easy to find , then , '' I remarked . `` Quite . At this hour and until twelve o'clock , M. de Marsan will be occupied in copying a document which I desire to possess . At eleven o'clock precisely there will be a noisy disturbance in the corridor which leads to the main staircase . M. de Marsan , in all probability , will come out of his room to see what the disturbance is about . Will you undertake to be ready at that precise moment to make a dash from the service staircase into the room to seize the document , which no doubt will be lying on the top of the desk , and bring it to an address which I am about to give you ? ''