Louis, Francis, Bill, and Zoey, and Ellis, Rochelle, Coach, and Nick have returned, though probably not in the way you'd hope for. The Left 4 Dead survivors have found themselves transported back to Nazi Germany to tackle those dreadful Nazi zombies in Zombie Army Trilogy. A free update last night added the eight survivors to Zombie Army's character lineup for your undead-redeading enjoyment.

To celebrate this merging of zombworlds, the game's on sale on Steam this weekend.

Zombie Army Trilogy, if you haven't seen it before, combines the two co-op-oriented spin-offs from Rebellion's straight-faced Sniper Elite WW2 FPS series, along with a new third chapter. It revamped the first two games a little, and the third added - of course - a burning demonic zombie Hitler.

Until Monday, a 66% discount makes Zombie Army Trilogy £10.19 on Steam or £30.59 for four copies so you can play with your pals.

Rebellion have also come up with a comic explaining how this lot ended up in another silly situation, though you'll need to install their 2000 AD mobile app to do that. A shame they wouldn't just dunk it on the web like Valve do, but hey, it's important to remember your #brandsynergy.

Left 4 Dead takes on Zombie Army Trilogy - Official Steam Update Trailer Watch on YouTube