u/Topmostbruh

The culprit changes the temperature of someone's room so that it gets really hot. Maybe by changing some panel settings, maybe by using a black cloth to trap heat inside of their room, I don't know yet. Because of this, that person is going to drink an absurd amount of water giving them water poisoning, and eventually killing them.

Once the victim has taken in enough water, the cculprit reverses the climate control changes.

The next morning, the victim wakes up with personality changes and a headache, and then dies during the day.

The culprit might manipulate the school so that it looks like an ordinary poisoning (but that would be refuted by there not being a poison that would kill that long after ingestion).

The case would be solved by finding out the poisoning was a water poisoning in the first place, that the victim drank that much water because of the change in temperature, and who made the changes that made the temperature go up by so much in the victim's room.

Any ideas for improvement?