The multiplayer game The Ship will be available for free via Valve's Steam service between December 22 and 26.
The Ship is the debut title for Outerlight Limited, and is built on Valve's Source engine. The main site for The Ship boasts that the "game challenges you to kill or be killed. Once you're on board you're given the name of another passenger whom you must find and secretly murder."
The game has both single- and multiplayer modes, and is available for pre-loading on Steam starting today. Outerlight is also offering a $5 discount for anyone who purchases the game over the free trial weekend or any time during the week that follows.