Zhang Heng did not know where Holmes had disappeared again. On the other hand, he managed to find a few prostitutes who were relatively close to the three victims, and through them, found out about their daily routines.
In the end, Zhang Heng set his sights on a man called Mark Cohen, a Jewish doctor active around the Whitechapel area. He wasn't a qualified doctor registered by the Central Medical Commission, but it was also rare that prostitutes were offered the luxury of getting a qualified doctor to treat them.
