You don't just stumble upon a kindred spirit every day. In a new promo video for The Passing -- Left 4 Dead 2's new chapter available today on the Xbox 360 and PC -- it takes an apocalypse to bring Francis and Rochelle together. Well, that and their shared "glass is half empty" outlook on life.

The Passing also kicks off a brand new weekly event in Left 4 Dead 2: Mutations. These are one-off custom game types created by Valve, with a different game type available each Thursday. Today introduces Realism Versus: a match of Versus with Realism enabled, making it much tougher to play as a Survivor and a heck of a lot easier to play as an Infected. In this mode, Valve anticipates the Jockey will be one of the most effective Specials.