I AM SPOOKED LATELY, REASON BEING, I HAVE THREE CATS AND SOMETHING UNKNOWN TO ME, I DO NOT SEE A THING BUT SOMETHING HAS THEIR ATTENTION FOR SURE. THEY ARE EITHER IN A DEAD STARE OR THEIR EYES ARE FOLLOWING SOMETHING.
Sorry for the delayed response as your question was just sent to me. Cats have heightened senses of hearing and smell compared to humans. They may sense something outside or rodents or insects that you do not see. Their specialized senses result in them focusing in on something to stalk or hunt it.