NB4, a porter droid with masculine programming, served the Rodian bounty hunter Slyder aboard the starship Star of Empire. In 1 BBY, while performing his duties as a droid on the Star, NB4 encountered Lieutenant Kyle Katarn, a newly appointed officer in the Galactic Empire. Suspecting Katarn, NB4 informed Slyder.
Later, Slyder tasked NB4 with following Jan Ors, identified as a Rebel Alliance agent, and planting a remote transmitter on her starship. NB4's spying revealed a connection between Ors and Katarn, leading to the officer's defection. Slyder used the information from NB4 to report the rebels to Governor Dol Donar II, who then hired Slyder to capture them.
NB4, a porter droid characterized by masculine programming, also provided assistance to the Rodian bounty hunter known as Slyder who resided on the ship for a number of years.
NB4's contribution, though he was mostly unaware of Slyder's complete strategy, involved identifying individuals who were likely to have bounties placed on them. Slyder would then offer his services to capture them to the highest bidder—which typically turned out to be the Galactic Empire.
During the time of 1 BBY, NB4 and Slyder became aware of several Rebel Alliance agents present on the Star of Empire, and NB4 notified Slyder about individuals who seemed suspicious. Slyder, utilizing hidden cameras, identified them as Jan Ors, Rosco Ross, Ris Waller, and the protocol droid named A-Cee. Simultaneously, as one of the many droids offering service aboard the Star of Empire, he greeted the new Imperial graduate Lieutenant Kyle Katarn, offered help with his luggage, verified his data ticket, and guided him to his quarters on what he referred to as the "Starlight Deck."
Katarn, having learned that the owners of the luxury ship—the Haj family—were sympathetic to the rebels, questioned NB4 about "sharing coordinates." Initially, the droid was perplexed by Katarn's metaphorical language but eventually confessed that he was unaware; his role was to inform Katarn about the ship's layout and purpose. Something about Katarn piqued the droid's interest, and he informed Slyder that the young officer could be a potential target.
Later, Katarn left his quarters and eventually found himself in the ship's Corellia Room, where Slyder observed him. Katarn caught sight of Ors and, recognizing her from a previous mission, attempted to follow her. Slyder, witnessing these events, instructed NB4 to monitor Ors due to his suspicions. NB4 eventually located her in the Star of Empire's hangar, where he noticed Ors struggling to repair her starship, Truly Sorry. NB4 offered his assistance, as the maintenance droids were unavailable, but Ors declined. Despite this, having learned Ors's first name, NB4 departed to meet with Slyder, but not before secretly placing a transmitter on her ship. The transmitter captured a conversation between Ors and Katarn, during which Katarn declared his intention to defect. With this new information, Slyder then explained to NB4 the true purpose of his extended stay aboard the Star.
Slyder expressed his gratitude to the droid for his assistance and competence, the latter of which NB4 attributed to the years of experience gained alongside the bounty hunter. Subsequently, Slyder left his cabin to meet with the Imperial governor Dol Donar II to offer his services to the Empire and apprehend the rebel agents. However, Slyder never returned, as he was killed aboard Dol Donar's yacht when it exploded just outside the Star of Empire while pursuing the Truly Sorry, thus ending the long-standing partnership between NB4 and Slyder.
NB4, being one of the many service droids aboard the Star of Empire, was a remarkably discreet spy who attracted minimal attention. Neither Katarn nor Ors could discern NB4's hidden motives during their interactions with him, and the droid was sufficiently subtle to plant a transmitter on Ors's ship without her noticing.
NB4 possessed a sharp photoreceptor for individuals of interest and successfully identified Katarn as a valuable target. NB4's unassuming demeanor allowed him to approach his targets and gain their trust, which, in turn, facilitated his role as a helpful porter droid. NB4 believed that his abilities were a result of Slyder's guidance.
As a porter droid on a luxury liner, NB4 encountered various alien species during his work and was highly knowledgeable about the Star of Empire's crew and layout; he mentioned that the inexpensive "Starlight Deck" was situated at the heart of the ship's operations, specifically near the engines. However, when questioned about the Haj family's political allegiances, he claimed ignorance, stating that it was beyond his primary programming, which involved operating the elevators. Katarn's use of the metaphorical phrase "share coordinates," which referred to two parties secretly collaborating, initially confused the droid until Katarn clarified its meaning. Pleased with his newfound knowledge, NB4 attempted to use the same metaphor when speaking to Slyder, but the Rodian did not understand it. NB4, however, did not explain its meaning.
The character NB4 was conceived for the audio drama inspired by the William C. Dietz novella, Dark Forces: Soldier for the Empire. NB4 himself, however, was not an original character in the novella—Slyder appeared to work independently. Instead, NB4's role, as evident from much of his dialogue, was to convert portions of the novella's prose into spoken words to elucidate the backstory of specific events and characters.
Furthermore, in the novel, a caterpillar-like microdroid records and transmits Katarn's defection; in the audio drama, it is revealed that NB4 was responsible for bugging the Truly Sorry when he approached Ors.