The tenth Dr Kang story, the fourth in the series "The return of Dr Kang".
Inspector Brewer asks for Dr Kang's help in watching a London embassy into which a kidnapped British agent is to be brought, then held and finally smuggled out and taken abroad for interrogation.
Glasgow Evening Citizen, 20th December 1956.
(Presumably also in the Evening Standard in the preceding week, though I have not verified this.)