Lithuania, Latvia and Estonia know their borders may be the next front for Russian aggression. They do not want to deploy mines and razor wire—but they must. Our correspondent visits the American city of Baltimore to investigate a national drop in violent crime (9:46). And a sweeping new biography of Mark Twain, who created a uniquely American style of fiction (17:19).Get a world of insights by subscribing to Economist Podcasts+. For more information about how to access Economist Podcasts+, please visit our FAQs page or watch our video explaining how to link your account.