Zer0 Sum

Plot
(Spoilers Ahead)

(Also, the game takes place after the events of Borderlands 2)

the story begins in Medias Res, On the planet Pandora, Rhys is seen trying to find Fiona until he runs into a unknown man in a black suit.

After being knocked out and tied up, the mysterious man drags Rhys across the wastelands and ask him about the Gortys Project. But Rhys just says, "that was just bad business". Afterwards the stranger asks Rhys to explain how he got in this situation:

Rhys, hoping to get a promotion in Hyperion, finds his former boss has been replaced by his nemesis Vasquez, who demotes him to janitor. Overhearing Vasquez making a deal for a Vault Key for ten million dollars, Rhys and his co-workers, Vaughn and Yvette, plan to make a deal to get the Vault Key first, using Hyperion funds to do so. Rhys and Vaughn arrive on Pandora, and after accustoming themselves to the violence, meet with the dealers, August and Sasha, to trade for the Vault Key.

During this time it is reveled that the Stranger has also captured Fiona for unknown reason; But after Rhys and Fiona are reunited, they are not happy to see each other. The Stranger then asks Fiona to explain her side of the story.

They are unaware that Fiona, Sasha, and Felix have created a fake Vault Key, and used August's reputation to assure Vasquez would be interested. Just as Rhys, Vaughn and August discover the Vault Key is a fake, the meeting is crashed by a fight between Bossanova and Zer0; Bossanova grabs the briefcase with the money and flees;Also leaving a vengeful August behind, who swears revenge against Fiona and Sasha for their con. After the group gets away from Bossanova, Rhys and Vaughn take shelter with Felix, Fiona, and Sasha as to track down the money, with neither side trusting the other. Rhys attempts to use a Hyperion ID drive, which he retrieved earlier from the corpse of Professor Nakayama at the deal location, but it causes him to black out and hear a mysterious voice taunting him.

At Bossanova's base, a former Atlas facility, Felix stays with his vehicle as the others are inadvertently split into two; Rhys and Sasha enter the base via an underground vent, while Fiona and Vaughn accidentally find themselves in a bandit death race, learning the briefcase is the prize for winning the race. As the race proceeds, Zer0 arrives and disrupts the race while attacking Bossanova, causing the briefcase to be tossed around between various trucks until it is caught by Felix. Fiona catches up to him, realizing that he has turned on her, but when he opens the case, a biometric security bomb inside detonates and destroys the money. Felix either dies in the explosion, or manages to throw the case away from him and escapes). As the four regroup, they find a secret chamber in the Atlas base, including a strange device that displays a map to a new Vault on Pandora. As they look, a mysterious voice speaks to Rhys, telling him this is part of the "Gortys Project". As he turns around, he is surprised at the sight of a hologram of Handsome Jack.