We'll finally understand why Ellie carries a burden like survivor's guilt in The Last of Us downloadable content episode, Left Behind, which now has a launch trailer.

The trailer can be viewed above and features the same kind of somber, wistful atmosphere as the main game. This is a prequel to Ellie's adventures of survival with Joel and will clue us into the kind of person she was before we got to know her.

In Left Behind, we get to meet Riley, Ellie's best friend. We'll help these two teens try to survive in a world that's become devoid of any hope, where monsters lay around every corner. But more importantly, we'll get a deeper insight into what makes Ellie tick as a person.

The download is a whopping 5GB and will cost $14.99, so prepare both your hard drives and wallets. It launches today on the PlayStation Store.