February as a rule is not a month of fogs, but rather a month of tempestuous gales, of frosts and snowfalls, but the night of February 17th, 19--, was one of calm and mist.

It was not the typical London fog so dreaded by the foreigner, but one of those little patchy mists which smoke through the streets, now enshrouding and making the nearest object invisible, now clearing away to the finest diaphanous filament of pale grey.
Sir William Bartholomew had a house in Portman Place, which is a wide thoroughfare, filled with solemn edifices of unlovely and forbidding exterior, but remarkably comfortable within.

Shortly before eleven on the night of February 17th, a taxi drew up at the junction of Sussex Street and Portman Place, and a girl alighted.

The fog at that moment was denser than usual and she hesitated a moment before she left the shelter which the cab afforded.
She gave the driver a few instructions and walked on with a firm step, turning abruptly and mounting the steps of Number 173.

Very quickly she inserted her key in the lock, pushed the door open and closed it behind her.