Valve has said to expect "new game modes" in The Passing DLC for Left 4 Dead 2, which is now listed as "spring" rather than March.
That's according to an update to the Left 4 Dead blog which lists some of the pack's new features.
These also include a "Wicked Witch Bride", an M60, a golf club melee weapon and "The Fallen Survivor".
Plus there's the chance to rendezvous with the L4D1 survivors. A separate L4D1 DLC pack will be released later that shows some of those story elements from the first game's perspective.
Check out our news from the other day to be reminded of The Passing's tagline, although beware that the previous announcement constitutes a bit of a story spoiler, in case you're squeamish about that sort of thing.