Does a compare/contrast essay have to have a contrastive aspect to it?

For the first compare/contrast essay, we were given topics to choose from for Macbeth, and they were all comparing two characters who were different. Now we have to compare a certain archetype between two stories of our choice, and we have to create the topic of comparison or contrast. I found two stories: "Macbeth" and "Lamb to the Slaughter", in which there is the archetype of appearance vs. reality, yet I can't find any way they contrast. Can it just be a comparative essay in which both stories show the same theme, and the thesis would be that they show the theme of appearance vs. reality?