There’s nothing quite like the comforting feeling of seeing an old friend after some time apart. This is the sentiment the Valve evokes with Left 4 Dead 2’s first batch of downloadable content, The Passing, bringing the characters of the first game into the environment of the second. Sure, the meet-up occurs in the midst of a zombie apocalypse, but in this case, it’s still quite enjoyable. The Passing brings more than just a good dose of nostalgia to Left 4 Dead 2, though; the new campaign and weekly multiplayer mutations add hours of gameplay and even further increase the replay value of the already fantastic title.