uncle invented a time machine, the Time-Conveyor. Daleks stole the Mark One model, hoping to reverse-engineer their own time machine from it.
Peter and his brother David pursued them through time in the Mark Two. They finally recovered it in Pompeii during the eruption of Vesuvius on 24 August 79, having defeated the Daleks one-by-one along the way. (PROSE: Timechase)