Smith and two colleagues then went to Ruislip to see the Krogers. Claiming to be investigating local burglaries, they gained entry to the house. Once inside, they identified themselves as Special Branch officers and said that the Krogers had to accompany them to Scotland Yard for questioning. Before leaving, Mrs Kroger asked to be allowed to stoke up the boiler. Before she could, Smith insisted on checking her handbag. It was found to contain microdots, the photographic reduction of documents to make them small enough to be smuggled more easily. Smith, a veteran spy catcher, had guessed her intention to destroy these microdots.