Left 4 Dead 2: The Passing
Torchlight.
The twist is that the first game's survivors actually provide serious support with high-calibre, laser-sighted weaponry, but they only cover the area immediately surrounding the generator itself. Gathering the 16 cans required to power it becomes a matter of launching miniature expeditions out to collect them, then hoofing it back as fast as possible either with either a can of gas in your hands or a surge of infected at your heels. If two Tanks do attack (did I mention you can get attacked by two Tanks at the same time?) your only chance of survival is to flee back to your new friends for some help. There's actually an achievement for letting them bring down a Tank alone.
It's a characteristically dramatic ending, but in terms of straight horror the campaign peaks with the Historic River Tour that sees you hiking through a couple of massive, water-filled chambers. There's no cover and no holding back as you push through the stagnant lagoon, zombies surging in from every angle, and on Realism mode you're especially screwed since you can't see more than fifteen feet in any direction. Pro tip: turning flashlights on and off is a good way of signalling your position.
The new campaign's a solid enough addition, if a brief one. The new Mutations mode is a little harder to judge. As I said before, each week it's going to change into a new game mode (the previous game mode being lost to the ether), and there's a special achievement for playing six different Mutations. So, something to encourage players to drop into L4D2 at least once a week.
This week's mutation is Realism Versus, giving you the chance to try L4D2's Survivors Vs. Infected mode with all the masochistic twists of Realism mode. To recap, that means Survivors get no indication of each other's locations, items don't get an outline and zombies are tougher to kill without a headshot.
The weird thing is, I'm sure a lot of people are going to prefer Realism Versus to Versus mode; the survivors are forced into playing a much more close-knit, careful game where even Rambo players can't afford to go off by themselves, and the Infected team get a more satisfying time of it too. The fact that the survivors don't have their trademark ESP means that rather than adopting damage-focused kamikaze tactics, you can bide your time before launching an attack on the last player to, say, round a corner.
And yet, Realism Versus isn't going to be here in six days. It'll be replaced by something else, maybe the Chainsaw Massacre mode Valve has mentioned and that we know nothing about. Mutations might be a great way to get people talking and have them coming back at least once a week, but I'm not sure it's the cherry on the cake that The Passing needed to be a must-buy add-on.
Instead, what you've got here is a reasonably priced chunk of content that doesn't quite breathe new life into Left 4 Dead the way a new Special Infected or a bigger, brighter new campaign might have. If you're still really hungry for more Left 4 Dead, The Passing won't let you down. If you think you've had your fair share, you might want to pass.