SF Short Story Identification: Boy finds a cube, people disappear, and boy becomes cube?

Question

I'm trying to search back up a short story that I read on the web. It's about a boy who discovers a cube, and when he picks it up, strange things happen.

• Things randomly transform into other things, and people slowly start vanishing or transforming into objects.
• The boy is the only one unaffected, and soon the town becomes unrecognisably surrealist.
• One scene in particular involves the boy warning a girl not to ever touch the cube, which she obeys for a long time. Unfortunately, the boy returns home one day to find the girl missing, and a doll with her exact features lying next to the cube.
• Secret agents from the state arrive, and they take away the boy from his family and perform psychological tests on him for years.
• The opening scene was the front lawn/garden of the boy's house, and there was this line that kinda went "The box was just suddenly there" on the grass/path.
• There was some kind of town gathering going on (maybe a carnival or a garage sale) and the incidents started affecting the neighbours a little while after the boy picked up the cube.

I forgot what happens after that, but I remember that the ending scene is that

the boy ends up in a small boxed space, and above him, another young boy peers down (hence looping the entire story).

Any help would be appreciated!

Answer 1

That's "Deus Ex Arca" by Desirina Boskovich, available online in its entirety here or here. Has all the elements you describe: the boy discovers a strange box, it causes strange transformations in others who touch it but does nothing to him, government agents come to investigate when he takes the box home, he tells his sister Emily not to touch it but eventually he just finds a doll in her place, etc.