H.G. Wells' the Invisible Man

Gambling losses lead one of Peter Brady’s staff, Smith, into selling information to a foreign power. A new top-secret rocket is being taken by road for test firing off the coast of Scotland and Smith has disclosed the time and route. Brady’s suspicions are around when he learns the schedule has been changed at the last minute and the journey has started earlier than arranged. He gives instructions for the envoy truck to be halted…but it has disappeared.