The recovering Reid arrests Lady Vera Montacute, an aristocrat who enjoys slumming it, who has been found unconscious in a Whitechapel lodging house next to the corpse of flower seller Ida Watts. Both women were drugged and Ida's cousin Tom Denton, a known thief who drugs his victims, is also brought in. He explains that he procured Ida for sex with Lady Vera and her husband, who arrives at the police station demanding his wife's release. Lady Vera admits to the murder but the modern finger-printing device proves that hers was not the hand upon the fatal weapon. When Abberline intervenes Reid realizes that he may not be able to make an arrest after all.
—don @ minifie-1