I think my cat may have eaten one of my Tylenol tablets that…

I think my cat may have eaten one of my Tylenol tablets that I set out on the night stand next to my bed. Do I need to worry? Is Tylenol toxic to cats?       Is 1 tablet enough to cause toxicity to an average cat? What will you advise this owner to do?       For 2 extra credit points, what are signs, symptoms of acetominophen toxicity in cats