midnight
`` Certainly . '' He snatched it from her in his eagerness , and smoothing it out upon the table he drew over the lamp and examined it intently . I had left my chair and was gazing at it over his shoulder . The envelope was a very coarse one and was stamped with the Gravesend postmark and with the date of that very day , or rather of the day before , for it was considerably after midnight . `` Coarse writing , '' murmured Holmes . `` Surely this is not your husband 's writing , madam . '' `` No , but the enclosure is . ''