After the Doctor damaged a camera in the Big Brother house, he was forcibly evicted. However, the disintegrator/transmat booth shut down before it vaporised the Doctor and the door to the outside was opened, proving that someone somewhere had arranged for the Doctor to appear on the Game Station. As the Doctor fled, he urged Lynda to come with him. After getting out of the Big Brother house, Lynda revealed that the Fourth Great & Bountiful Human Empire had deteriorated even further 100 years previously, back when the Doctor destroyed the Jagrafess.
Later on, after Rose Tyler's apparent disintegration, Lynda, the Doctor and Jack Harkness invade Floor 500 and there they discover the truth. The Controller was responsible for bringing the Doctor to this timeline, knowing that he would be capable of stopping the Daleks who had been manipulating the Human Empire for the past few centuries from behind the scenes. Jack also revealed - using Lynda as a guinea pig - that the Game Station's disintegrator array was actually a transmat and that contestants weren't killed but teleported across space, meaning that Rose was still alive.
In "The Parting of the Ways", Lynda remains on the Game Station so that she can help the Doctor in defending the station from the Daleks. Jack assigns her to a monitor station where she can observe the Daleks' movements, but unfortunately the Daleks find her. One Dalek squad attempts to break into the room Lynda is in by cutting through the reinforced door, but three more Daleks appear outside the window, hovering in space. With a silent exclamation of "EX-TER-MIN-ATE", the lead Dalek fires through the window and the decompression blows Lynda out into the vacuum of space.