During the Clone Wars, the Galactic Republic initiated a mission with the objective of demolishing a Confederate listening post situated on the planet of Vanqor. However, Jedi Master Quinlan Vos, who was secretly in the service of the Separatist leader Count Dooku, divulged classified details about the impending operation to the Separatists. Consequently, the Separatists were successful in evacuating the listening post significantly in advance of the arrival of Republic forces. Upon the arrival of Republic and Jedi forces, they discovered the listening post had been completely deserted. This situation resulted in the Jedi Order developing a strong suspicion that they had a mole operating within their organization.
Following a failed Jedi and Republic operation aimed at extracting vital supplies from a Separatist supply storage base, Jedi Master Quinlan Vos was commended for his role in safeguarding his Jedi comrades by alerting them to the presence of concealed bombs within the asteroid base. Recognizing his worthiness to combat the Separatists, the esteemed Jedi High Council entrusted Vos with leading an operation focused on the destruction of a Separatist listening post located on the planet of Vanqor. Previously, Quinlan had been captured during a mission with the objective to assassinate Count Dooku, and he subsequently endured several months in Separatist imprisonment. Under the alias of "Admiral Enigma", Vos acquired an extensive understanding of Separatist military tactics.
For this particular assignment, Master Vos was accompanied by Master Obi-Wan Kenobi and the Jedi Knight Anakin Skywalker. Unbeknownst to the Jedi, Vos had succumbed to the allure of the dark side of the Force and had become Dooku's Sith apprentice. In reality, this was merely a deception employed by Vos to manipulate Dooku into leading him to his master Darth Sidious, with the ultimate goal of eliminating the Sith once and for all. To perpetuate the facade of unwavering loyalty to Dooku, Vos intentionally leaked crucial information regarding the planned operation to the Separatists. Consequently, Dooku was able to orchestrate the complete evacuation of the listening post before the arrival of Republic forces.
Anticipating significant resistance from Separatist droid fighters, Kenobi, Vos, and Skywalker piloted three Eta-2 Actis-class light interceptors. They were supported by twenty-four ARC-170 starfighters, which formed the initial assault wave. As they descended into Vanqor's atmosphere and neared their designated target, the three Jedi were perplexed by the complete absence of any opposition. While the Jedi and the vanguard approached the listening post, Kenobi instructed Admiral Block to deploy the second wave, suspecting a potential Separatist trap.
As the Jedi starfighters drew closer to the listening post, Vos "remarked" that it appeared to be deserted. To confirm this assessment, the three Jedi starfighters executed a strafing run to potentially dislodge any remaining individuals. Although their blaster fire destroyed the listening post's primary dish and tower, their sensors failed to detect any ships, vehicles, individuals, droids, or wildlife in the vicinity. Subsequently, the Jedi landed at the listening post, where they were joined by several Clone troopers under the command of Clone Commander Cody. Following a thorough inspection of the interior, the Jedi and clones concluded that Count Dooku had somehow acquired intelligence about the operation and had orchestrated the facility's evacuation. As a result, Kenobi and Skywalker rightfully began to suspect the presence of a traitor within their ranks, responsible for divulging information to the Separatists.
In the wake of the unsuccessful Vanqor operation, the Jedi Order began to harbor suspicions that a traitor was actively leaking sensitive information to the Separatists. Due to Master Vos' previous captivity under Dooku, Quinlan Vos became the primary focus of these suspicions. Following a private discussion with Vos, Master Yoda was able to discern that Quinlan had indeed succumbed to the dark side. Uncertain whether this indicated a complete allegiance to Count Dooku, the Jedi Council entrusted Vos with a mission to assassinate Dooku. Success in this endeavor would be considered a sign of innocence, while failure would serve as conclusive evidence of his treachery.
After obtaining intelligence indicating that Dooku's Providence-class Dreadnought was scheduled to visit Christophsis, Vos and his lover Asajj Ventress journeyed there aboard her vessel, the Banshee. Unbeknownst to Vos, the Jedi had dispatched Kenobi and Skywalker to discreetly monitor his movements. Utilizing a stolen Separatist shuttle, the two Jedi managed to follow Vos onto the dreadnought. There, they discovered Vos attempting to coerce Dooku into leading him to his master Darth Sidious. Confronted with irrefutable evidence of Vos' betrayal, the two Jedi promptly placed him under arrest. However, Vos and Dooku successfully escaped, leading to a Republic assault on Christophsis.