It had started to rain;

Harry put on a burst of speed and zoomed toward the other end of the
pitch. He could hear the Bludger whistling along behind him. What
was going on? Bludgers never concentrated on one player like this; it
was their job to try and unseat as many people as possible ...

Fred Weasley was waiting for the Bludger at the other end. Harry
ducked as Fred swung at the Bludger with all his might; the Bludger
was knocked off course.

"Gotcha!" Fred yelled happily, but he was wrong; as though it was
magnetically attracted to Harry, the Bludger pelted after him once
more and Harry was forced to fly off at full speed.

It had started to rain; Harry felt heavy drops fall onto his face,
splattering onto his glasses. He didn't have a clue what was going on
in the rest of the game until he heard Lee Jordan, who was
commentating, say, "Slytherin lead, sixty points to zero.'

The Slytherins' superior brooms were clearly doing their jobs, and
meanwhile the mad Bludger was doing all it could to knock Harry
out of the air. Fred and George were now flying so close to him on
either side that Harry could see nothing at all except their flailing arms
and had no chance to look for the Snitch, let alone catch it.

"Someone's - tampered - with - this - Bludger -" Fred grunted,
swinging his bat with all his might at it as it launched a new attack on
Harry.

"We need time out," said George, trying to signal to Wood and stop
the Bludger breaking Harry's nose at the same time.

Wood had obviously got the message. Madam Hooch's whistle rang
out and Harry, Fred, and George dived for the ground, still trying to
avoid the mad Bludger.