Doctor Who: Vanderdeken's Children

It is 3123, and traveling in the Tardis into deepest space, the Doctor and Sam find three spacecraft. One is a Ximosian warship, the other an Emindaran civilian starliner, and the third a ship of strange allen design. Both Ximosian and Emindaran crews want to discover what cargo this strange structure holds.In attempting to discover where these vessels come from, the Doctor and Sam unearth a terrible truth. The aden ship is caught in a closed loop of time, being neither created nor destroyed, constantly circling the vortex. The Doctor wants the ship to be destroyed, but the Ximosian and Emindarans are caught in a wrestle for power, and both desire to possess the spacecraft and transform its power into a source for their own political ends.