How would you finish this werewolf story....?

Question

A boy from Florida is sent to live with his grandparents in Maine after his parents were killed in a car accident during a birthday trip to Disney World. The boy was the only survivor, but he had massive leg injuries which now requires him to wear leg braces, making him unable to run and hard to walk. 
Granddad is patient while Grandma is easily annoyed and really religious, but both are overprotective and won't let the boy go outside by himself, and since they have a lot of farm work to do; the boy spends most of the time in his room.Late one night, as he looks out his bedroom window, he sees a werewolf prowling outside. The creature tries to get in the barn after livestock, but it's padlocked shut as a precaution from Granddad, who says he doesn't want them stolen. The werewolf spots the boy and, feeling hungry, climbs up a trellis to the second story window. He breaks the glass and is halfway inside, but gets a surprise attack by Grandparent's cat, the boy's only friend. The werewolf runs off as the grandparents rush in. Grandma blames the boy for the broken window, but Granddad thinks it's strange the window is broken from outside and convinces his wife not to punish him. The Granddad doesn't say anything, but finds claw marks and black fur caught in the window frame.Is one of the grandparents the werewolf? An escaped ex-con?A hobo? Just a stranger? Will they ever find out? What do you think should happen next? How could this story end?

Elaine M · Answer

We don't use the word hobo anymore,  not since the 1950s.

Zac Z · Answer

I'm not going to suggest an ending for this story - it's your story.

But I'll say that this is one of the better story ideas I've read here. Given sufficient suspense of disbelief necessary for that genre (which I have, being a genre fan) what you wrote doesn't have too many of the usual gigantic plot holes, inconsistencies and or other nonsense.
Yet, some things don't add up for me, so you might want to think about that. (Or not, your choice.)
1. "... he sees a werewolf prowling outside..." - how does he know this is a werewolf? Don't werewolves normally look like proper wolves (during the "wolf phase")?
2. A wolf climbing a trellis... doesn't sound too convincing. (I'm also wondering about the ratio of human thoughts vs. animal instinct. An animal, even a hungry one, wouldn't climb to the second story to try to eat a boy; a human being should be clever enough to try to avoid further detection and disappear quickly. It would be less implausible if the boy's room were on the ground floor.)
3. The episode with the cat is BS. Sorry but that doesn't fly. I have a VERY hard time believing that a cat would attack a wolf; I think, a cat would try to get the hell away as fast as possible from an attacking wolf. And a wolf would not be scared away by a cat either.
4. "an ex-con" - where did that one come from all of a sudden? Is there are prison nearby? Why would a werewolf be an ex-con? Just because werewolves are generally seen as bad creatures and you think all (ex-)cons are bad people? Is there some mechanism that turns people into werewolves that is more prevalent in prisons? I don't see the connection here other than awfully clichéd stereotyping. Drop the ex-con, please.

Lastly, if this is a story as in "short story", this could work with some tweaking if you find a good ending. Frankly, it's really not that bad and I've read worse in published anthologies. I'm talking about the story, not the writing of which we haven't seen anything, of course.
But if this story is supposed to be a book, you just have the beginning.

EDIT:
"The boy knows the creature is a werewolf because it looks like one, according to all the comics the boy reads."
OK, it's your story but I'd say that this is fine for a story target at a young audience but a mature one would probably have questions.
Does a werewolf look significantly different from an ordinary wolf? That one is easy. If you decide so, the werewolf looks different. Full stop.
But why do the folks making comics know that? Do they have first-hand knowledge of actual werewolves? Really?
Is it coincidence? That's a weak concept.
Another option would be that the boy is mislead by the clichéd conceptions in the comic and the "werewolf" isn't a werewolf after all. That one is a somewhat clichéd trope in itself but resolves the "comic problem". At the same time it flips your entire story idea on its head, so probably not a good solution.
Anyway, that's my two cents. I don't want to harp on these points, just wanted to give you some feedback. Maybe other people wouldn't have these questions.
As a last thought, I'll say that many is prepared to forgive certain weaknesses in the story if the story is otherwise well done. If you start critically dissecting them, many stories turn out to be not 100% logically sound. That doesn't excuse sloppiness on your part but there might always be some weaknesses.