Well I thoroughly enjoyed that! It's a nice idea, good plot. I like the normalcy of the day's events; how Lily was trying to make the holiday as normal as possible, following traditions, which Halloween is full of really. It was very simple, yet unique. A classic one-shot that was entertaining and light to read. Plus, I always enjoy a good Lily/James story, they're my favourites.. :)
As for criticism, many of your sentences seemed to run on, some of them would have been better as two sentences, or with just a comma, but it wasn't too recognizable, and there were only a few.
I'm not sure if you're one of those people who try and use britishisms? I'm not saying you have to be, or that you're wrong, just wanted to point out a couple of things you could have changed if you wanted to, but you don't have to concern yourself over this as its entirely the author's choice, just some people prefer to have british words thrown in there somewhere. So for example, you could have changed yard to garden, couch to sofa even.
There were a few places where it would have sounded better to add a joining word in, like and, or as:
..onto the Evans' windows, how she always managed to put one or two up on the dormitory... it sounds like there should be an 'and' in between windows and how.
..Then, sudden as a gunshot.. There should be an 'as' in between then, and sudden.
There weren't many spelling errors at all, only reentered is re-entered, and equaled is equalled.
Your grammar structure, other than some of the sentences being too long, is good. It was actually very well-written, just a couple of mistakes here and there, but they aren't noticeable, and it's only because I went over it a couple of times that I spotted them. :P
I really liked it, you did a good job. Congratulations for finishing the challenge, first to finish it too. :) It was a creative way to come at the challenge, and I like how you incorporated things that are so happy and things that are so dark and upsetting in one story, in such a short period of time, during Halloween. I didn't really think about the deaths of Lily and James when I created the challenge, but I really liked this, so I'm glad someone did! But I just thought I would let you know that I thought that was some good bit of thinking on how to turn a challenge that was created with happiness and festivities in mind into something with the perfect balance to it, creating a great story and an interesting response to a challenge in one go. You should be proud of this, as I'm very proud that I inspired it. :P
I hope to get back to you as soon as possible with the winners, but as you finished so early, that won't be for a few weeks. Good job once again, and thanks for the good read. :)
Author's Response: Thank you. Thank you, thank you - I definitely can't say it enough. Reviews like this make me want to keep writing; I'm reminded of why I love doing this. I'm so glad you liked the story! I am quite proud of this, it's one of my favorite things I've written. :D Thank you for the challenge! I'll be awaiting the results excitedly.