Written in the stars
Our tale starts in the Forbidden Forest. Barty has been given a special assignment from the Ministry, to track down and kill every Centaur in the forest. He has no idea why, but if he fails to do so, the Minister won't be happy.
Barty preferred Muggle weapons when hunting magical creatures. So, as the first Centaur approached him, he aimed his bow at it and fired.
The arrow hit the tree beside the Centaur and it smirked. "Not a very good shot, Mr. Hunter."
Barty lowered his bow and scowled. "Bartemius Crouch Sr. is my name, Head of Magical Law Enforcement at the Ministry of Magic."
The Centaur said, "Firenze." He then asked, "What crime have my herd and I committed, Mr. Crouch?"
Barty admitted, "I don't know."
He threw his bow and quiver of arrows to the ground and muttered, "The Minister never told me."
Firenze told him, "He thinks that we will join He Who Shall Not Be Named, but we won't. We're going to fight with Harry Potter and his friends, not against them."
Barty frowned. "What am I even doing here? I was just about to exterminate a whole herd for no reason..."
Firenze smiled. "You had your own reasons, you trusted the Minister."
Barty stated, "I will never trust him again."
Firenze beamed, "This meeting is going according to plan."
Barty gasped. "You knew that I was coming here?"
Firenze nodded and merely explained, "It was written in the stars and they're never wrong."
Barty chuckled. "You Centaurs are strange creatures, but you fascinate me."