Was the boy trying to copy something he read in a comic book? In another type of book?
Was the boy trying to copy something he saw on T.V.?
Was the boy trying to copy something he saw in a movie?
Did this take place after 2010? After 2000?
Comic book, though I think unclear if it is the book, a tv show, or a movie. But something seen in a comic book(or a movie/tv-show of one).
I believe after 2010. After 2000 for sure.
Was an animal or animals involved?
Was the chemical produced by plants?
Was the chemical produced by organisms, including bacteria etc?
Did the arm go to the chemical, such as by putting his arm in something?
or
Did the chemical go to the arm, such as by smearing the chemical on his arm?
Was the chemical in liquid form?
Was the chemical in solid form?
Was the chemical poison ivy?
Was the boy trying to develop a resistance and/or immunity to the chemical?
You know what? It’s basically solved except the details. I don’t see any reason for people to keep guessing.
A Korean boy showed up with ulcers on his arm. He apparently injected mercury into himself to gain the powers of either Wolverine(the adamantium) or a hero named Mercury. I’ve read both versions.
Oddly enough, the same boy had previously allowed spiders to bite him to become spider-man-like.
Mental problems, for sure.
If a superhero villain called “The Mad Hatter” appears in the next few years, we’ll have our likely culprit, along with origin story.
Kind of a classic, so if you know it, zip it. 
A man hired a small crew to sail his yacht from New York to Florida(he had a vacation home in Florida). The man flew down to Florida and waited for his yacht, but when it did not arrive in a reasonable amount of time, he called the Coast Guard. Sure enough, the Coast Guard found the yacht…but not the crew. What happened?
Was illegal activity involved?
Specifically, was smuggling involved?
Was all of the crew (presumably) alive and well?
When the yacht was found, was it on the open ocean?
Was it in dock, harbor, dry-dock, or a similar situation?
Was the yacht still seaworthy?
KK
Was all of the crew alive?
Was any of the crew alive?
Was any of the crew well?
Were any of the crew mentally unwell?
Was the yacht on the open ocean at the time the crew left it?
Did the crew transfer to some other vehicle?
Was the crew of sufficient size to man the yacht?
Was this a motor vessel or a sailing yacht?
How far off-shore was the yacht discovered?
KK
Were the crew experienced sailors?
Is it known for certain what happened to them?
Is their fate speculative?
Did the crew get drunk?
Did the crew fall unwell?
Were the crew poisoned? If so was it deliberate? Accidental?
KK
Was the ship up to modern safety standards?
Did all crew members die at the same time?
Were the bodies eventually found?
Did the crew leave some message behind which explains what happened?
Are weather conditions relevant? Was it fair weather? Fog? Storm? Did they run into some unexpected natural phenomenon like a waterspout?
This one is probably answered by your negative reply to Chronos’ question about vehicle transfer, but just to make sure: did the yacht, when recovered, still have all its lifeboats attached?
Was some other item missing which should have been there, and might give a clue to the fate of the crew?
Did the crew all go swimming at once, whether accidentally or deliberately?
KK
Was this event the inspiration for a movie?