While good-ness is difficult to define in the Fallout series, evil has - until recently - been pretty clear-cut. Sure, the Enclave was intent on rebuilding America, but doing so by wiping out everyone and everything that isn't 'pure' and completely radiation-free is just a bit of an 'Adolf' way to go about it. Yes, the Enclave - made up of the descendants of high-ranking politicians and former presidents of America - was a nasty piece of work beneath those eloquent, creaky facades. Though you don't really need to know the Enclave's questionable principles to know they're evil; in a world filled with dishevelled, scrappy-looking people, anyone who goes around wearing a suit and tie is bound to be evil, right? Just look at Half-life 2 and The Matrix. But after the events of Fallout 2 and Fallout 3, The Enclave is pretty much extinct, existing - as far as we're aware - only in the kind of remnants that we see in New Vegas. The Fallout 4 trailer suggests its place could be taken by 'The Institute', a faction that creates androids that are as emotionally intelligent as humans, then uses them as slaves. We know that this mysterious organisation will play a big part in the story, but knowing the Fallout games, it seems likely that you'll have some control over whether you side with them or against them.