A story in which Harry learns the important lesson: When you jump to conclusions it's hard to get back.

Harry Potter was not a student known for his brains. He was, however, well known for his impulsive need to help those he thought were in danger. So naturally, while perusing the Marauder's Map one night, upon discovering that Oliver Wood and Marcus Flint were in an otherwise empty classroom together, he assumed the worst and dashed off to see if he could help his fellow Gryffindor.

Soon enough, under his trusty invisibility cloak, Harry stood in a corridor on the fifth floor of the castle, listening for any sign of a fight from the two boys the map was telling him were on the other side. Oddly enough, though, all was silent from the classroom. Just as Harry was beginning to assume that he had either misread the map, or that nothing bad was happening to Oliver at the hands of Flint, he heard a crash followed by a loud thud from the other side of the door. His determination rekindled, Harry nudged the door open a little bit before promptly closing it again, turning a spectacular array of reds, and running back to Gryffindor tower. Because Harry had been quite wrong about what Oliver Wood and Marcus Flint were doing in an empty classroom together. They had not been, as would be expected, fighting, and what Harry had seen was something much different. What he had seen was Marcus Flint pinning Oliver Wood to the teacher's desk (which Harry would never be able to look at the same way again), and kissing him passionately, while skillfully relieving him of his trousers. Which, to Harry's innocent 13-year-old brain was more horrific than if they had been fighting. And so Harry learned a valuable lesson that night, about how one should never jump to conclusions, because it's intensely hard to get back.

And the next day during quidditch practice, no one could figure out just what it was that was making Harry turn that shade of red.