The story:
Dave Palmer sends Captain Byron and his "wife' Diana on a military mission to take a dispatch case with secret papers to the coast, but a spy ring working for an enemy power has intercepted the communication and swaps the real case for a fake.

Returning to Diana's house for a last look at what he forlornly thinks is his lost lover, the Phantom manages to recover the real case and attempts to reach Byron and Diana before their train reaches the coast. But the resourceful and deadly spy gang is close on his heels...