[[!meta title="Deepest Fear"]]

Third year, but the dementors don't stop the train on the way in to Hogsmeade.
As a result, Harry does not have his encounter with the dementors, and the
boggart he sees in Lupin's class is not a dementor - it is Vernon, calling him a
freak and threatening to beat him and lock him in the cupboard again.

As a result of the very public outing of Harry's living conditions, Lupin and
Harry's friends set about getting him removed from the Dursleys permanently.

* This probably needs the relatively common conceit of Harry's treatment at the
  Dursleys involving physical beatings.
* Could go either clueless!Dumbledore or manipulative!Dumbledore.
* The boggart happens relatively early in the year, and if it's revealed that
  fear is why Harry never strives to do well in school, he could still change
  classes.