Murder at 3 am 1953

Source: DVD 576p 3,000 kbit/s. There have been a series of murders of young women, and the police commissioner is demanding results from the detectives. A common feature is that they all took place at 3 am, and the victims were leaving clubs whose names seem to follow a pattern - P, L, A, Y - What next? But then an aged waterman puts the detectives on to another common factor - the dates were all of high tide on the River Thames.