‘Twas more than a year ago that Left 4 Dead 2’s Cold Stream DLC first stirred beneath the grave of Valve’s nearly immortal undead sequel, and then – as though cast in the world’s most anticlimatic horror movie – it just kind of sat there. “I’ll rise and kick off the end of all human civilization tomorrow,” it thought to itself. But tomorrow never came. Until now! After gobs of testing and fine-tuning, Valve’s finally deemed Cold Stream fit for public consumption.