Suspicion of foreign espionage, cursive messages in ancient Chinese, a sensitive microchip — and a suspect that could not be stopped at the border. Ravindar Patil, the assistant Mumbai police sub-inspector assigned to the case, was scratching his head for answers. But first, he had to find a place to lock up the unusual captive. So he turned to a veterinary hospital in the Indian metropolis, asking it to retrieve a list of “very confidential and necessary” information about the suspect — a black pigeon caught lurking at a port…