"Left Behind," the single player expansion pack for the smash hit "The Last of Us" title will be coming to the PlayStation 3 and PlayStation 4 as a standalone download, according to Sony and game developer Naughty Dog.

The expansion deals with events before those that unfolded in the main game. In "Left Behind," main protagonist Ellie and her friend Riley sneak out of their boarding school and explore an abandoned post-apocalyptic mall. The prequel will eventually disclose the incidents that prompted Riley to join the Fireflies. 

According to Arne Myer, community strategist at Naughty Dog, the title will allow players new to "The Last of Us" to explore events that lead to the infection, and the events unfolding for the prequel are as riveting and sad as the main title's.

Myer said, "While part of the story of Left Behind takes place during the main narrative arc of The Last of Us, I think some of the best and most touching moments of any game in recent memory occur during the prequel segments, as we follow Ellie and Riley." 

As part of the standalone title, unique content will be added to expand the players' gaming experience. There will be a free two-hour trial of the Factions multiplayer mode for both PS3 and PS4. For those who would want to get the full version for the multiplayer, upgrade paths will be included in the game's store. Upgrades include a full digital single-player game with Treacherous Territories map pack and the full Factions Multiplayer mode. 

The standalone "Left Behind" title, prequel to "The Last of Us," will be released on May 12 for the PlayStation 3 and PlayStation 4.