When Marty gets ahold of a page from the diary of his sister, Erica, he expects to find a bunch of brags about what it's like to be the better Pants sibling. But what he discovers instead is something HUGE. Erica's written a secret about who or more accurately, WHAT Marty actually is. And though the page is torn in half, Marty, through his unique deductive skills, determines that he is undoubtedly a big-toothed, sharp-clawed, hairy-faced werewolf! Now it's up to Marty to save his neighborhood from the greatest danger of all, himself!