This short story, entitled "The Red One," can be found in the anthology From a Certain Point of View. Rae Carson is the author of this tale, which is centered on the droid known as R5-D4.
R5-D4, a member of the R5 unit line, has spent the last four years effectively as a "prisoner" of a Jawa clan. This clan roams the Tatooine deserts aboard their sandcrawler. R5-D4 yearns to be free of the sandcrawler by being sold off to a new owner. He craves a little lubricant and, more importantly, a sense of purpose. One evening brings him joy as two Jawas examine him, determining that he is finally ready for sale. They lubricate his joints, remove sand from his tool compartments, and clean his photoreceptors. Some hours later, R5 is awakened by the beeping of R2-D2, who was captured by the Jawas following the events of the secret mission to Tatooine. R5-D4 observes as the protesting R2 is fitted with a restraining bolt.
Later that same night, R5-D4 is once again roused, discovering that R2-D2 has tried to damage him. When R5 confronts him, R2 reveals that he is on a crucial mission, explaining that he must escape the sandcrawler and be sold the next day, as the fate of the galaxy hinges on it. R5 inquires if this was the reason his pincer was deep inside his access compartment, and R2 replies that the Rebellion requires his assistance. The word "Rebellion" stirs a faint memory within R5, but he retorts that he will cease to function if he doesn't escape the sandcrawler and find a new master. R2 responds that he already has a master, and that if he doesn't find him, the galaxy is doomed. As Jawas approach, R2 assures R5 that he won't try to harm him again.
The next morning, R5-D4 and R2-D2 are brought to the Lars moisture farm, the residence of Owen Lars and his adopted son Luke Skywalker. After bargaining with the Jawas, Owen decides to purchase R2's companion C-3PO and R5. While R5 is ecstatic, R2 becomes anxious; R5 assures him that someone will eventually buy him. When R2 tells R5 that he is his only hope, the red droid understands the importance of R2's mission, and decides to sacrifice his new opportunity by destroying his own motivator. R5 intentionally loosens his head plate and redirects the lubricant behind his photoreceptors. Once the lubricant is heated sufficiently, R5 deliberately discharges the power, causing his head plate to fly off. Luke then believes that R5 has a faulty motivator. Owen thinks that the Jawas are trying to cheat him and instead chooses R2, thereby setting the stage for the events leading to the Battle of Yavin. Before they part ways, R2 thanks R5 for helping him save the galaxy, and promises that he will never forget him.
R5-D4 understands that R2-D2's story is true when Imperial stormtroopers later attack the sandcrawler. The stormtroopers question the Jawas about the droids they sold, and then proceed to kill them. R5 survives the massacre by concealing himself within the junk that the Jawas had collected. He then escapes the sandcrawler and makes his way to a settlement, hoping that one of the moisture farms in the next valley will take him in. Having been inspired by R2, R5 also hopes to join the Rebellion.