Don't Mind the Ghost, He's With Me

You're having a grand ol' adventure, spelunking down a ravine into a dark cave, then delving your way into a massive dungeon full of traps and dangers and then one of your friends disappears. And no one says a word about it. Nobody's worried. Why not? Cuz his player just couldn't come to the game, that's why!

If you've played tabletop rpgs at all, you've probably come up against this problem. Obviously, you're part of a gaming GROUP and you'd like the entire group to show up to any given session. But it's also very awkward narratively speaking. Where did the party member go? Is he there, but a shade of his usual self, barely participating (another player calls the shots) and never really interacting? What if he is killed while his player wasn't there? How do groups handle this?

No game unless
An easy solution is not to get together unless everyone can make it, but schedules being what they are, especially in the adult world*, that's often easier said than done. You might never be able to play. And say you do get make a date and someone opts out at the last minute, say to rip up a carpet, do you send everyone home? A good GameMaster and open-minded players can get around this by playing a pick-up game outside the bounds of their usual campaign, either with the same system or another.

Nomads, shnomads
The best technique - the one *I* use, at any rate - is to avoid games/stories that take characters on long journeys together. Basing your campaign in a specific city or area to which you always return makes justifying a character's absence fairly easy. He or she is at home, or otherwise occupied, because characters with homes have lives. Nomads have lives, sure, but even downtime is spent "in-game". Think of it this way: If you go on a road trip with your friends, you have to spend every waking moment with them. If you're just going out in town, some of the gang might not show (in fact, that's why you're having the player problem in the first place!). It, of course, doesn't fix the problem of cliffhangers. If a specific scenario takes more than one session to resolve itself, absentee characters will throw a spanner in the works, especially if they were motivating the story.

I am become as unto a god!
While players may not be the best choice for handling a friend's character (they already have their hands full, will rarely role-play the other character except to make fun of it, and might even use it as cannon fodder), the GameMaster is already used to playing a full cast of characters. Turning the PC in an NPC doesn't interrupt the flow of the game, and the GM can make sure the poor soul doesn't get killed or give his stuff to an unscrupulous player's character. The character could even be used to prod solutions out of the party when they're stuck, though it would normally be pretty unimaginative under the GM's direction.

Retcon
If nobody ever mentions it, it's like they were never there in the first place. Somebody else picked up the map fragment. Somebody else's grandma has been captured by Doctor Dangerous. We were always known as the Two Musketeers. Not narratively satisfying, but let's just get on with it.

The plot device
Finally, there are always some old school solutions like taking the character out from an injury or trauma. Stuff him under a bail of hay in the wagon and hope for the best. That's how Eric Stoltz survives Anaconda. It shouldn't be too hard to leave a character behind to the ministering care of a good Samaritan in most games. The most extreme example of this I've seen is characters being turned into ghosts. They were there, but hardly visible and not tangible. How or why was never explained to me. I guess it's Retcon with special effects.

What do YOU do when that slacker/elven ranger doesn't show up?

*Ha! That'll teach you to play games after you're out of high school!