On the Planet Pandora abandoned by Dahl Corporation,Four Vault Hunters,Brick,Lilith,Mordecai,& Roland arrive in search of the fabled Vault. After discovering the town of Fryestone,the Vault Hunters begin to receive psychic instructions from a mysterious woman,the Guardian Angel. The Vault Hunters meets the robot,Claptrap & a doctor,Zed,who help them establish a reputation by killing several bandit leaders,eventually leading to the collection of an alien artifact, being the first piece of a key needed to open the Vault.
Patricia Tannis, Dahl's former archeologist still in residence on the planet,contacts them,revealing that the Vault can only be accessed once every 200 years & that the time of the next opening is approaching. She also explains that three more artifacts are needed to complete the Vault Key. Meanwhile,Commandant Steel of the Crimson Lance threatens to declare martial law & demands the Vault Key pieces.
The Hunters secures two more pieces,but one was in possession of the bandit lord Baron Flynt. Steele contacts the Hunters to reveal that there are in fact only three pieces & that Tannis has betrayed them. He then disables the planet's ECHO network, preventing further communication with the Guardian Angel & anyone else. The Vault Hunters infiltrate the base & find Tannis imprisoned. She claims she was forced into betrayal & urges them to restart the ECHO network & stop Steele and the Crimson Lance before they can reach the vault. After restoring the network, the Guardian Angel directs the Vault Hunters toward Steele's location.
The Hunters encounter Crimson Lance forces already locked in combat with the Vault's alien Guardians. Steele uses the Key to open the vault,releasing a giant monster,the Destroyer. Steele & the troops gets wiped out. The Guardian Angel explains that the Eridians created the Vault to imprisoned the Destroyer. The Hunters manage to defeat it. The Guardian Angel is revealed to be transmitting her signals through a Hyperion satellite in orbit high above Pandora. The signal was send to Claptrap on the planet.
