four o’clock in the
    afternoon
This is what he says : ``` MY DEAR MR. SHERLOCK HOLMES , -- Lord Backwater tells me that I may place implicit reliance upon your judgment and discretion . I have determined , therefore , to call upon you and to consult you in reference to the very painful event which has occurred in connection with my wedding . Mr. Lestrade , of Scotland Yard , is acting already in the matter , but he assures me that he sees no objection to your co-operation , and that he even thinks that it might be of some assistance . I will call at four o'clock in the afternoon , and , should you have any other engagement at that time , I hope that you will postpone it , as this matter is of paramount importance . Yours faithfully , ``` ROBERT ST. SIMON . ' `` It is dated from Grosvenor Mansions , written with a quill pen , and the noble lord has had the misfortune to get a smear of ink upon the outer side of his right little finger , '' remarked Holmes as he folded up the epistle . `` He says four o'clock .