From the back cover:
"The Agent 13 Sourcebook allows Top Secret/S.I. game players to enjoy the pulp-adventure action of the 30's. Enter the world of diabolical villains, beautiful (and deadly) dames, courageous heroes, and improbably escapes. The Brotherhood plans to bring the world to it's knees - can you stop them?
The Agent 13 Sourcebook also includes a coplete background for other adventures in the 1930s, allowing you even more roleplaying variety: G-Men on the trail of gangsters, masked crimefighters going where the law can't reach, fearless explorers discovering lost civilizations, and tough private eyes who'll take any case if the money is right.
And, as always all this excitement is presented the way you've come to expect it from Top Secret/S.I. products: Easy to play, yet chillingly realistic. You'll feel the gangster's tommy gun in your back, you'll hear the fiendish laugh of itsu, the Hand Sinister. So pack that .45 underneath your coat, snap down the brim of your fedora, and come along..."