How do people act toward the end of the plague?

This depends on what point of the story you are referring to. In the beginning H.F. begins by relating rumors that the plague had come to Holland, and closely follows the bills of mortality. Certain parishes are affected, but cold weather seems to stave off the worst of the plague during the winter. However, in May and June the numbers of dead begin to swing upwards and H.F. starts to wonder whether or not he should leave the city. After some debate back and forth, he decides that God wants him to remain.

Well at the end of the narrative, the people, for a while, felt as if the plague was all gone and became careless which spread the disease even further.