It depends on the journey. Every Northern Belle journey returns within the day.
Lunch and afternoon tea journeys are circular: the train travels a scenic route and returns to your departure station without stopping. You can't get off along the way.
Day trips stop at the destination for your visit, then return, usually to the station where you boarded. Check your itinerary, as some journeys end at a different station.
Each journey page shows provisional departure and return times for every boarding station; your travel documents confirm the final timings. If you're arranging onward travel home, allow for possible delays on the rail network.