The Walking Dead: Season 1 game from Telltale Games, is currently Free on Humble Bundle's Store. The game is free to promote an end of summer sale, where you can get many games for steep discounts.
If you are a fan of the comes (or the TV show), or horror games, The Walking Dead: Season 1 should be an interesting game for you.
And just like the other games from Telltale, this is also an episodic interactive drama graphic based on the comic book series. There are 5 episodes in the game, where you can follow the story, make your choices in dialogue options. The game features quick time events where some action is involved, and the decisions you make are carried over from one episode to another. So if a character likes the protagonist, and you make a bad decision, it could end up with them disliking you, and so on.
Go to the Humble Store page for The Walking Dead Season 1. Click on the "add to cart" button, and checkout for free. (requires an account). Then go to the downloads page and get the key which you can then redeem on Steam.
The giveaway is active till September 9th.
The Walking Dead 400 Days DLC is NOT included in this giveaway. And make sure you redeem the key before September 23rd.