|Location of Event :
||Alpha / Delta Quadrant 
|Stardate of Event :
||79900 approx and 54973 approx 
|Nature of Event :
||Alternate timeline 
On the tenth anniversary of the U.S.S. Voyager's return to Earth in 2393, Admiral Janeway embarked on a conspiracy to alter the timeline in order to return the ship to the Alpha Quadrant early. Janeway was dissatisfied with the way in which events had unfolded on Voyager; in the original timeline her close friend Seven of Nine had died in 2380 after being injured on an away mission. Seven's husband Chakotay had been grief-stricken by the loss and had never fully recovered. Commander Tuvok also did not fare well in this timeline; he developed a neurological condition in 2377 which could only be cured by a mind meld with a compatible Vulcan. Since none were available in the Delta Quadrant, Tuvok's condition gradually worsened until he was largely incoherent.
Twenty two Voyager crew members had been killed between 2377 and the ship's arrival at Earth, and although most of the crew went on to live happy lives Admiral Janeway had become a much more cynical person after the journey.
She acquired a tachyon projector from the Klingon government through Ensign Miral Paris, daughter of Voyager crew members Tom and B'Elanna Paris, and a supply of the drug chronexaline from Joe, the Voyager EMH, in order to allow her to survive using the device to go back in time.
Before she could go back in time the USS Rhode Island, a Nova class vessel under the command of Captain Harry Kim, apprehended Admiral Janeway but she was able to convince Kim to allow her to proceed with her plan. Janeway successfully travelled back to 2377 and met with Voyager. She gave the ship complete access to the technology of her shuttle, including transphasic torpedoes and the ablative armour generator.
Using this technology Voyager penetrated a nebula in which they had previously detected dozens of wormholes. They had investigated the nebula only to find dozens of Borg vessels there, and had rapidly retreated. Now fitted with technology twenty five years in advance of their own, Voyager was able to batter her way through the Borg and reach the centre of the nebula. There they found not wormholes, but a transwarp hub - a set of gateways into transwarp conduits which allowed the Borg to reach any part of the galaxy in just minutes.
Realizing that Admiral Janeway had lied to her, Captain Janeway withdrew from the nebula. Despite her older self's advice, Janeway decided to destroy the transwarp hub whilst within the conduit in an attempt to both reach home and deny the Borg further use of the network. The two Janeway's hatched a plan by which they could do this; the Admiral infected herself with a neurolytic pathogen and allowed the Borg Queen to assimilate her whilst Voyager returned to the transwarp hub and headed for Earth. With the Queen destroyed and her Unicomplex damaged, Voyager was able to successfully destroy the hub whilst heading for Earth.
Unfortunately, a Borg sphere managed to catch up with the Starship. Captain Janeway allowed it to bring Voyager aboard, riding ahead of the shock wave all the way back to the Alpha Quadrant inside the sphere. Once clear of the conduit, Janeway destroyed the sphere from the inside and sailed clear of the wreckage to be greeted by a Federation fleet.
Although Admiral Janeway's actions were clearly illegal and immoral, her plan brought Voyager to Earth sixteen years early, allowed Tuvok the chance to seek treatment for his condition before it could become serious, saved the life of Seven of Nine and twenty one other crew members, and gave the Federation technology that has put it decades ahead of the other major Alpha Quadrant powers. As such, it can only be called a success.