"Come, see what manner of labour you're taking on yourself," said Cadfael cheerfully, and downed his spade to take the new boy around the enclosed garden, showing him the vegetables, the herbs that made the noon air heady and drunken with fragrance, the fish ponds and the beds of pease that ran down almost to the brook. The early field was already dried and flaxen in the sun, all the harvest gathered, even the later-sown hung heavy and full of pod."
Notice how not only the cheerful Brother Cadfael, but the time of day and year creates a lighter mood. Although by the title the reader knows it's going to be a mystery with dead bodies, one still doesn't feel the underlying horror one felt from the first scene in the Follett book.
A well woven plot and believable characters are important to any story, but so is the sense of place against which the plot and characters are woven and sometimes writers seem to overlook the importance of sense of place.