I don’t often get to check both of those categories.  Valve has created a Left 4 Dead comic… really a whole 178-page graphic novel.

Use fire, Bill! Oh, you know already.

(Spoilers ahead, so read this later if you have to.)

It’s pretty good. I don’t entirely care for the art style, but it’s well written, and chock full of meaty information if you’re interested in the L4D1 characters.  It has some backstory on all of them (Francis was going to jail, who could’ve seen that coming?), and covers the interval between the army rescue at the end of Blood Harvest and the new campaign, The Sacrifice, which in turn intersects with the L4D2 campaing The Passing where both sets of survivors meet.

Most interestingly, it addresses some puzzles set by L4D2.  At the end of  The Parish, the military on the final bridge asks the L4D2 survivors if they’re “immune”, which they carefully distinguish from “not infected”.  Graffiti on the walls in L4D2 also talk about carriers and suggest that these are being shot by the military.  So how do you distinguish carriers from immune, which are our survivors, and if the military thinks they’re carriers why do they bother letting them across the bridge at all?

The comic pretty well clears this up.  There’s a test for the virus– and the L4D1 survivors are carriers.  Chillingly, they may have helped spread the zombie virus.  (As Francis points out, the news chopper pilot had been bit; but they may well have infected the other pilot.)  And that in turn means they can’t get to whatever safe havens remain; thus Plan B… finding a zombie-free island. 

I’m still unsure what made many graffiti-writers in L4D2 so sure they weren’t carriers.  We’re told the virus keeps mutating… even if you got tested that wouldn’t be much assurance.  But it’s realistic enough that people would cling to the idea that they were immune, on good evidence or none at all.

Actually the comic implies that there are three classes of non-zombies: immune, asymptomatic carriers, and susceptibles.  The latter are just those who haven’t encountered the virus yet; naturally you won’t find any more in an infected area (including saferooms).  Presumably many of the remaining safe havens are mostly populated by susceptibles. 

The comic also explains what seemed like a dumb bit of  The Crossing: why didn’t the two teams of survivors join together?  The L4D1 survivors said they preferred being on their own; this fits in with Bill’s insistance in the comic that they stand by each other– and leave everyone else (4 dead) if necessary.  In their circumstances trusting other people may no longer be an option– plus there’s the frightening chance that they might infect someone new.  (Though if they’ve been fighting their way through the South, Coach et al. must not be susceptible.)

Presumably we’ll find out eventually what happens to the L4D2 survivors after their own ‘rescue’ by the military.  And presumably we won’t learn more about Zoey, Francis, and Louis.  (Without Bill they’re not even suitable for new L4D1 campaigns.)  They make it to the island; no hint of the remaining key question: who does Zoey make it with?