The Swarm remained dormant in the TARDIS' computer until the Doctor's seventh incarnation. Shortly afterwards, the Doctor returned to Titan Base in the company of Ace and Hector Thomas in 4920. The TARDIS had been commandeered by Hector, who had fallen under the control of the Swarm. It ensured its own creation by returning to the Bi-Al Foundation, where it mutated from the Saturnian plague.
While in 4920, the Nucleus cloned itself and uploaded its mind to the Bi-Al Foundation computer. It then used the TARDIS to travel forward in time to the 52nd century, by which time the centre had become a Hypernet relay station. Using the TARDIS' Relative Dimensional Stabiliser and the power of the Hypernet, it intended to recreate itself and become corporeal. However, it was defeated by the Doctor, Ace and Hector. (AUDIO: Revenge of the Swarm)