What's The Best Way To Leave A Role-playing Game? Reviews RPG & Card Board
If in an awkward position for the character to just up and go do something else, I'd suggest giving the Dungeon Master the reins for a bit. The character is still there, if perhaps not as forward as normal, then departs for whatever else is pulling him off when an opening occurs.
Of course, there is always the possibility of just having him killed off. Character death is always good RP fuel, especially if the GM is given enough of a heads up to work it into the story.