Hugh North 04: The Yellow Arrow Murders, by Van Wyck Mason (epub/Kindle/pdf)
In the bay of Cienfuegos, a little Cuban town, the naked body of a D.C.I. officer was found floating one night. And the next, Captain North of the Army Intelligence was on his way there -- with orders to find the facts. The wolves of the naval powers were already gathering at Cienfuegos around a cashiered American naval officer who had developed a new and mysterious invention. And beside the agents were the great international criminals always drawn by such an affair. The first intimation of the sinister undercurrents North was facing came on the night train in Cuba -- when a drab-looking German was murdered almost before his eyes, with a glass dagger thrust into the heart. At Cienfuegos the real battle began, with danger lurking in the surrounding jungle, and within the house death striking with silent arrows -- so much quieter than automatics, so much easier to use from a distance than knives...