Fleetward had discovered crystals around the world which, once assembled, would resemble a human skeleton. He was afraid to reveal his findings, which indicated the crystals were formed before humans even existed on Earth. The Doctor gave him information on where to find other crystals, and convinced him to show the assembled skeleton at an exhibition at the Institute on 31 January 2004.
The Council of Eight determined Fleetward was a threat to their plans, so they sent one of their Agents to kill him at the exhibition. Sabbath shot it with a Vortex Gun, delaying it long enough for the Eighth Doctor to send Trix and Fleetward to the far future through the time corridor in which the Agent had travelled.
The two found themselves on the space station at the centre of the universe, right before the Big Crunch. They were pursued by the Agent, who captured them and put them in a Schrodinger Cell on the Council of Eight's Time Station. Later, Octan released them, as well as Richard and Edward from another cell. He ordered them to kill Trix and Fleetward, but they refused. This caused a series of events which led to the downfall of the Council.
After returning Fleetward to his hometime, the Doctor convinced him to adopt the two boys, since history recorded that they had been killed in the 15th century when they came from. (PROSE: Sometime Never...)