“Can you suggest any possible motive for taking the papers to London except to sell them?”

“No, I cannot.”

“Then we must take that as our working hypothesis. Young West took the papers. Now this could only be done by having a false key⁠—”

“Several false keys. He had to open the building and the room.”

“He had, then, several false keys. He took the papers to London to sell the secret, intending, no doubt, to have the plans themselves back in the safe next morning before they were missed. While in London on this treasonable mission he met his end.”

“How?”

“We will suppose that he was travelling back to Woolwich when he was killed and thrown out of the compartment.”