B-4D4 was assigned the ID number 003127. He was the assistant to Jana Lorso and usually served as a greeter for visitors of the Czerka office, but also had access to the corporate computer mainframe.
The latter fact was discovered by Meetra Surik during her forced stay on Citadel Station. Interested in getting to the surface on the planet Telos, she agreed to help Chodo Habat and his Ithorians against Czerka, their competitors for the Telosian restoration project, in exchange for a shuttle off Citadel Station. By bribing a Czerka employee named Corrun Falt, promising him to search the mainframe for compromising evidence against Lorso, she learned that Opo Chano held droid repair credentials on B-4D4. After acquiring the credentials, the Exile entered the Czerka office and ordered the droid to follow her.
B-4D4 was taken to the Ithorian compound and reprogrammed, which freed him from his duty to serve Czerka and gave him the ability to lie. Taking advantage of this, B-4D4 was sent by Habat back to the Czerka offices where he persuaded Lorso to grant him access to the mainframe, saying that he had found inaccuracies in corporate accounts and intended to correct them in Czerka's favor. Once inside, he manipulated T1-N1, the utility droid in charge of the mainframe, into attacking Czerka employees and, in the resulting confusion and panic, not only downloaded the files bringing light on the corporation's illegal operations, but also erased all the data referencing his own purchase.
B-4D4 then delivered the files to the Ithorians. Habat then allowed B-4D4 to leave. However, Moza was unsure if it was wise to let him go, as he was now programmed to lie, a trait not expected in droids, thereby causing much trouble. B-4D4 assured them that he would not do such a thing, though whether he meant it or not is unknown. Understanding that that Czerka would likely discover what had happened, B-4D4 and T1-N1 waited at the docks for the first shuttle to Nar Shaddaa.
Originally, the player was supposed to meet B-4D4 and T1-N1 on Nar Shaddaa after leaving Telos. The corresponding conversation can be found in the cut content.
If the player has chosen the light side, then B-4D4 will temporarily join the player's party.
On Telos there is a man who will get angry when you search the apartment. When playing as B-4D4 you have the ability to threaten to kill him. B-4D4 will fight with his bare hands and will then receive dark side points. However, the experience from killing the man does not show up on B-4D4's character page. However, B-4D4 is not indestructible, so he will die if his hit points get low enough.
If the player has chosen to help Samhan Dobo with his smuggling (dark side) and has completed Samhan's first two smuggling quests, B-4D4 can be used in the third one, to steal medical supplies for Dobo and will be forced to fight a TSF officer. This contradicts Chodo Habat, who claims that B-4D4 can not harm a sentient being.
When playing as B-4D4, the player can blackmail Opo Chano and receive 20 credits. It is also possible to convince a protocol droid in the Dock Module that the station's leading council has granted Czerka the right to collect an excise tax on all incoming traffic, and that he, B-4D4 is in charge of collecting the tax. You do not actually get the profit from this, however.
If the player uses the first person viewpoint while playing as B-4D4 then the view is given a red-orange hue as if looking through B-4D4's photoreceptors.