Deus Ex: Human Revolution is a prequel to the first part of Deus Ex. To be precise, chronological prequel kicks off in 25 years (2027 th year) before the main events of Deus Ex. By the end of the show you will meet friends from previous installments of the characters and scenery. Although the gray haired to be a fan of Deus Ex is not necessary in the game a new protagonist, Adam Jensen, and new characters of the second plan. So if you do not know anything about the universe Deus Ex you will lose only a couple of minutes nostalgic sobs