The Passing brings Left 4 Dead 2's survivors together with three of the original gang--Bill, Francis, Louis and Zoey--with multiple new game modes, weapons and infected plus a new power ballad from the Midnight Riders, "Save Me Some Sugar."

While The Passing has been priced at 560 Microsoft Points ($7) on Xbox 360, Valve has yet to reveal whether the PC edition will also cost money or be free, as its updates have traditionally been on PC. More details on The Passing are promised this week.

Further content for the first Left 4 Dead was at one point due to arrive roughly a month after The Passing, telling of Bill and the gang's journey towards The Passing, though it's unknown whether this timetable has been revised in light of The Passing missing its original planned launch window of "late March."