Valve will offer a free, day-long Left 4 Dead trial tomorrow.
Steam users will be able to play the game from midnight tonight until midnight tomorrow, and the game can be pre-loaded now so you're ready when the clock strikes go.
The recently released Survival Pack will be included in the trial, which adds the Survival game mode and two extra multiplayer map.
In Left 4 Dead, a team of four survivors use teamwork to overcome a never-ending wave of Infected (zombies, basically) enemies. The twist comes from being able to control the Infected baddies during multiplayer. It's brilliant.
Creep over to our Left 4 Dead review to find out why.