In the year 19 BBY, Fives, an ARC trooper, managed to break free from the Grand Republic Medical Facility situated on Coruscant. This escape occurred after he was falsely accused of assaulting Supreme Chancellor Palpatine. Fives had been deeply involved in investigating the circumstances surrounding the perplexing mental breakdown of his comrade, Tup, a fellow clone trooper. This breakdown led to Tup's subsequent murder of Jedi General Tiplar during the Battle of Ringo Vinda. Aided by the medical droid AZI-3, Fives uncovered the existence of organic chips implanted within all clones. Following his escape from Tipoca City in a bid to prevent the Kaminoans from concealing the truth, he successfully convinced Jedi Master Shaak Ti to allow him to present his concerns about the potential danger of these chips directly to the Chancellor.
However, Palpatine was secretly the mastermind behind the entire plot, operating as Darth Sidious, the Dark Lord of the Sith. Once alone with Fives and his guards, Palpatine revealed the true purpose of the chips: to compel the clones to execute the Jedi. He then instructed the guards to eliminate Fives. Fives defended himself, but when Shaak Ti entered the room after hearing Palpatine's cries of apparent fear, it appeared as though Fives had attacked the Chancellor without provocation. Pursued by the Togruta Jedi, Fives fled, his aggression and paranoia intensified by a drug secretly administered to him by Nala Se, a Kaminoan scientist. He eventually arranged a meeting with his superiors, General Anakin Skywalker and Clone Captain Rex, in a warehouse situated on Level 1325, hoping to plead his case. Tragically, Fives was killed by the Coruscant Guard who tracked him to the location. Due to the drug's effects, Skywalker and Rex were skeptical of his claims, and Fives' death was attributed to a parasite that had caused his "inhibitor" chip to malfunction. The Jedi remained unaware of their impending doom.
During the Battle of Ringo Vinda, Tup, a clone trooper, began to exhibit peculiar behavior and suddenly killed Jedi General Tiplar amidst combat, thereby halting the Republic forces' progress. Without the awareness of the Jedi or his fellow clones, this was caused by a malfunction in Tup's behavioral modification biochip, a device implanted in all clone troopers to ensure their compliance with Order 66. Tup was subsequently taken back to Kamino for investigation. The Kaminoans, aware of the chips but believing they served as a safeguard against rogue Jedi, attempted to conceal their existence.
However, Fives, an ARC trooper and Tup's closest friend in the 501st Legion, grew suspicious and sought to uncover the truth. Tup passed away shortly after the removal of his malfunctioning chip. Fives, aided by the droid AZI-3, discovered that the chips were implanted in all clones during their embryonic development and had his own chip removed. After compelling Nala Se, a Kaminoan doctor, to acknowledge the existence of the inhibitor chips (though she claimed they were only meant to curb the clones' aggression), Fives convinced Jedi Master Shaak Ti to grant him an audience with Sheev Palpatine, the Supreme Chancellor of the Republic. Unbeknownst to Fives, Palpatine was secretly Darth Sidious, the Dark Lord of the Sith, and the architect of the entire conspiracy. After persuading Shaak Ti to allow her to accompany the Togruta Jedi and Fives to Coruscant, Nala Se secretly administered a drug to Fives that induced aggression and paranoia as they approached the city planet.
Upon the shuttle's arrival at the Grand Republic Medical Facility, Mas Amedda and Coruscant Guard troopers greeted Shaak Ti, Nala Se, and Fives. They escorted them inside to Palpatine, who was waiting with his guards. Nala Se explained that Fives had removed his chip, arguing that this made him a danger to himself. Released from his restraints on Palpatine's orders, Fives defended himself, asserting that the chips were intended for something else, given what had happened with Tup. Eventually, Palpatine ordered Amedda, Shaak Ti, and Nala Se to leave, claiming that Fives would feel more comfortable making his case in their absence and assuring them of his safety due to the presence of his guards.
Once only Palpatine, his loyal Coruscant Guard troopers, and Fives remained in the room, the Chancellor revealed the true purpose of the chips to the drugged Fives, along with his involvement in the conspiracy. He then ordered his guards to kill Fives, who retaliated in self-defense. Shaak Ti and the others heard the Chancellor shouting in apparent fear from inside and entered to find Fives grabbing a blaster and attempting to assassinate Palpatine. The Jedi Master used the Force to push him away from the Chancellor, and Fives fled through another doorway.
Knowing that his pursuers would likely disbelieve his claims about Palpatine attempting to kill him, Fives fled down a staircase, ignoring Shaak Ti's calls for him to stop. She followed him as he ran through a room filled with doctors, patients, and droids, roughly shoving people out of his way. However, when Shaak Ti ordered the blast doors closed, Fives managed to squeeze through the gap before the exit was sealed, much to the Jedi Master's frustration.
Because he had attempted to assassinate the Supreme Chancellor, a manhunt was launched for Fives. Although the Jedi had not been officially asked to search for the rogue clone, the Jedi Council dispatched Anakin Skywalker, Fives' commanding officer, to covertly search for him after Skywalker volunteered, along with Rex.
Fives eventually reached the clone trooper bar 79's, where he spotted Kix, a fellow member of the 501st, and followed him into the refresher. He asked Kix to contact Skywalker and Rex, providing him with coordinates for a meeting place on Level 1325, before slipping away unnoticed by Coruscant Guard troopers searching the establishment.
Skywalker and Rex arrived at an unoccupied warehouse, only to be trapped in a ray shield by Fives. Fives attempted to explain the truth about Palpatine and the control chips, but the drug administered by Nala Se impaired his ability to articulate himself clearly, making him sound deranged. When Coruscant Guard troopers led by Fox arrived in response to a sighting by a probe droid, the paranoid ARC trooper reached for one of Rex's blaster pistols and was fatally shot by Fox.
With both Fives and Tup dead, Palpatine attributed the events to a parasite the clones had contracted on Ringo Vinda. The Jedi remained unaware of the control chips that would ultimately lead to their demise.