Maybe it was the high bombardment of positive ions at the Eye of Orion or the prospect of a few days holiday. Or perhaps enough time had passed since Nyssa…
Whatever the reason, they were all actually happy and getting along - no bickering or complaining. Turlough wandered outside with a sketchpad to capture the scenery, Tegan disappeared into her room for a long, relaxing bath, and the Doctor redesigned the control room. He felt particularly proud of how the console turned out.
The Doctor smiled contentedly. They need this: a fresh start, a chance to put past mistakes behind them.