Facing mortality.

In one of the storylines I remember best Calvin found a wounded raccoon & brought it home. His mother knew it couldn't be saved as soon as she saw it, but took care of it for Calvin's sake. In the end Calvin learns about death & grief. Watterson regretted making this story, as there was little humor & no lightheartedness in it. It did touch people's hearts though, & was based on a true story.