In 3643 BBY, near the end of the Cold War between the Galactic Republic and the Sith Empire, the undercover Sith Lord Tarnis arranged for the kidnapping of his Republic scientist alter ego Eli Tarnis by the Black Sun criminal syndicate. With Tarnis's inside information, the criminal Zeer and his team infiltrated the Senate Building on the Republic capital of Coruscant and retrieved the doctor in the heavily-guarded structure. While Zeer and his men served as a distraction by barricading themselves in Docking Bay 84 of the nearby Coruscant Spaceport, Tarnis then escaped to the territory of his allies in the paramilitary Justicars' Brigade and continued his plans to acquire the Planet Prison superweapon.
In 3643 BBY, during the Cold War between the Galactic Republic and the Sith Empire, the Jedi Council sensed a disturbance in the Force on the Republic capital of Coruscant and dispatched the Jedi Master Bela Kiwiiks and her Padawan, Kira Carsen, to investigate. Kiwiiks was able to confirm the dark presence on the capital, though she was unaware that its source was in fact the Sith Lord Tarnis, who was posing as a Republic scientist named Eli Tarnis on the Republic superweapon initiative. Sensing that his position was compromised, Tarnis contacted the Migrant Merchants' Guild and Black Sun criminal syndicates, and arranged for the theft of the design files for Tarnis's project, the Planet Prison superweapon, in order to draw potential suspicion away from himself.
When a young Jedi Knight, the former apprentice of Jedi Master Orgus Din, was sent to retrieve the files from the criminals in the Old Galactic Market region, Tarnis contacted Black Sun's leader, Salarr. In exchange for Imperial weapons and technology, Tarnis requested that Black Sun conduct his "kidnapping" so that he could escape the Senate Building without suspicion and continue with his plans to acquire the Planet Prison.
Doctor Tarnis, the kidnapping's target
With inside information supplied by Tarnis, a team of Black Sun criminals under the leadership of the Human Zeer infiltrated the Senate Building, incapacitating the Coruscant Security Force officers and Republic Military personnel guarding the building, and Tarnis was quickly extracted by Zeer's team before alarms were raised.
However, the Security forces and agents of the Republic Strategic Information Service, the Republic's intelligence agency, quickly realized that Tarnis was missing. SIS Agent Galen immediately ordered Kira Carsen to lead a team of Coruscant Security officers to the nearby Coruscant Spaceport in pursuit of the kidnappers.
Tarnis left Zeer's group at the Senate Plaza and took an air taxi to Black Sun territory as planned, though he diverted his taxi to Justicar territory, a region of Coruscant under the control of the Imperial-friendly paramilitary Justicars' Brigade, where he continued his plans to acquire the Planet Prison itself. Zeer and his team barricaded themselves in Docking Bay 84 of the spaceport as a distraction, though Carsen and the CSF officers eventually broke the criminals' lines with the aid of the Jedi Knight who had been sent to retrieve the stolen design files. The Knight was later sent on a mission to rescue Tarnis from Black Sun territory, though Tarnis's deception and true identity was revealed during the rescue attempt.
Doctor Tarnis's kidnapping is first mentioned in Star Wars: The Old Republic, a video game released by BioWare and LucasArts in 2011, at the end of the Jedi Knight class mission "Stolen Secrets." The subsequent mission, "Kidnapped," deals with the pursuit of Tarnis's captors, but it is not revealed until the following mission, "The Rescue," that Tarnis himself orchestrated the kidnapping.