After an old lady commits suicide her heir accuses Gladys of having defrauded her, but soon realises her error and enlists Gladys's help in locating the real criminal. Trevor begins investigating, and discovers that other old ladies have also died in similar circumstances – two of whom were patients of Dr Shan, a Chinese healer. While Eavis arranges exhumations Gladys investigates Dr Shan, and his next potential victim turns to her for help – a timely decision, as her jewellery is stolen shortly afterwards.

When Gladys confronts Shan he takes her hostage at gunpoint and demands clear access to a cross-Channel ferry. Eavis arranges for his car to be decoyed aboard an empty ferry and then the police – including the Chief Constable – stall for time while Trevor sets up an outrageous pantomime with firecrackers and a Chinese mask which spooks Dr Shan into giving himself up.