The latest expansion to Civilaztion V added spies to the game.
These spies can help in a multitude of ways. The most important, in my opinion, being the ability to prevent enemy spies from stealing your technology. The main problem I have with this is that my single spy is struggling to prevent this theft, even with the Constabulary in place. The only other solution is to place additional spies in my high priority cities.
How can I get more spies?