A wave of mysterious robberies is sweeping the
country, and fifty thousand pounds' worth of diamonds has been stolen in six months.
During the fourth raid a nightwatchman is attacked with chloroform, and just manages to
gasp out 'The Green Finger' before he dies.
Chief Inspector Dale has heard the enigmatic
phrase before: it was the last utterance of a drowning man wanted in connection with
another robbery. But with no further leads, the police are baffled. The cry goes out in
the popular press: 'Send for Paul Temple!'