Valve is an extraordinary company. Despite Left 4 Dead 2’s success, the team continue to update its predecessor with bug fixes and brand new content; whereas other developers may have released The Sacrifice, the latest piece of downloadable content for the four-player zombie shooter, exclusively on Left 4 Dead 2, Valve have released the brand new campaign for the original Left 4 Dead and its sequel, giving both customer bases an opportunity to play this new chapter in the saga.

Those who play the new campaign on the original game will be struck by its appearance; while players of the game’s sequel will be accustomed to sunlit levels, it’s the first official campaign for the original game in which players can spot the Sun through the usual gloom of night. With one new campaign, Valve have dismissed the original’s clichéd settings – which were arguably part of the game’s charms in the first place, but will probably not be sorely missed. After all, if you don’t like the campaign, you can just play one of the five others available for the game.

If you’ve been reading the four-part comic based on this campaign, which has been published on the official game website in periodic instalments, then you’ll be aware of the campaign’s plotline. Valve truly outdid themselves with the comic, which added tons of character development and revealed a vast amount of back-story; unfortunately for players, the campaign’s supposed depth never shows in gameplay. The only gameplay mechanic we’ve never seen before is when a Survivor accidentally sends a pack of crows flying, and their cawing attracts infected – but even that was scripted.

Like every other campaign for the games, there are no cutscenes, and no particularly significant pieces of dialogue, although The Sacrifice boasts some of the most hilarious exchanges of brief conversation seen in the games. At one point, Francis reveals that he has “islaphobia”, or a fear of islands, and Louis swears to protect him from that “dumb punk-ass bitch island”. It’s these little exchanges that bring so much character into the otherwise lifeless characters.

Players who own the game on Steam will be pleased to know that the downloadable content is entirely free and downloaded automatically, so you really don’t need to worry about any potential cost (unlike Xbox 360 owners, who will need to pay for the new content). This includes the new campaign, the new maps for the other gameplay modes, and five new achievements.

The Sacrifice is likely the last piece of downloadable content we’ll see released for the original Left 4 Dead, and it leads seamlessly into The Passing, a campaign available exclusively for Left 4 Dead 2. It’s a great cross-over for existing owners of the second game and all the more incentive for others to finally bite the bullet, kiss the boycott goodbye and purchase the sequel.