On a warm day in April, two taxis pulled to a stop outside 221B Baker Street in London. The doors of each cab swung open and a girl stepped out of each. One girl was short and plump with curly black hair; the other was of average height with very straight light brown hair.
The cabbies helped their respective passengers unload a suitcase and each girl paid her cab driver. The dark haired girl added a generous tip; the light haired one a minimal one.
Four legs carried two bodies to the dark blue door of 221B. Two fists rose in unison and knocked.