Fog is define in two ways "a thick cloud of tiny water droplets suspended in the atmosphere at or near the earth's surface which obscures or restricts visibility" and "something that obscures and confuses a situation or someone's thought processes."
For this Challenge, use natures mysterious phenomenon to illustrate a lack of clarity. This could be physical, as in fog drifting through the trees, or abstract.
Don't have fog where you live? Experiment by breathing on your lens before taking a photo!