The Left 4 Dead Blog explains the mutation in the new automatic update for Left 4 Dead 2 that's now available through Steam as a free update for the co-op zombie shooter. The mutation is Follow the Liter, which returns from a previous go 'round which was not a rousing success, something they are once again blaming on the writers: "Week 3’s Mutation did not win over the crowds, but we think that’s because it was misunderstood. It has a very different feeling than Scavenge and games tend to be much lower scoring. You have to remember, if their can goes up in flames – they have to wait for it to respawn. So get that can on the ground and use the Spitter to light it up!"