Little Brother sees monsters everywhere, so he'd rather stay safely inside and read all about them in his books. Big Sister believes monsters are nothing but phony baloney make-believe and drags Little Brother on a hair-raising adventure to prove it. In a hilarious echo of common sibling squabbles that both older and younger siblings will appreciate, Little Brother has soon had ENOUGH of Big Sister trying to make him just like her. When Big Sister leads them into big trouble, it's time for Little Brother to show that he has what it takes to save the day.