0-18 or A Message from the Sky (1914)

Otto Bergmann and William Bergmann are (apparently) peaceful foreign merchants conducting a business as importing chemists in a strange land. Nevertheless they are important secret agents of their government and very clever ones too. The story opens just as a great war is about to begin between their own country and that in which they are doing business. The two Bergmanns with their porter and chauffeur as their assistants are holding themselves ready to do whatever the heads of their spy system demand of them. They are, however, closely watched by their stenographer, who is really "Operative No. 0-18," an agent of the Secret Service. She is in constant communication with another Secret Service Agent, a man. The Bergmanns receive a "Message from the Sky" to the effect that a certain time on a certain day a troop train will pass over a particular railroad bridge. They are instructed to blow up this bridge just as the train crosses over it. The "stenographer" and the Secret Service man, by a clever ruse, have placed a Dictograph in the Bergmann's private office. She overhears them planning but is herself caught with the receiver of the Dictograph at her ear. They render her unconscious and after devising a way to get rid of the Secret Service man, who they discover waiting outside, they carry her out as though she had fainted and take her away in their motorcar. They are followed by a motorcyclist, who is also a Secret Service man, who learns their plans and sets out in pursuit. Space makes it impossible to give in detail all the intensely exciting events that follow. The girl is saved in the nick of time and from the information she gives the Secret Service man arrives at the railroad bridge in time to save the troop train, the bomb actually exploding as it is thrown into the boat containing the spies.