Certainly a very interesting and complicated character in the story, Mr. Crouch has a very detailed backstory. He is first introduced when Harry and his friends go to the Quidditch World Cup at the beginning of the story, and Mr. Crouch comes to talk to them about the preparations for the World Cup. Right from the start, Mr. Crouch is distinctly calculating and cold, consistently goes for perfection, is lawful, and puts large amounts of emphasis on the rules, which is probably the strongest reason why Percy idolizes him. While seemingly boring at the beginning of the book, he starts playing a huge role as the story progresses.
In Chapter 27, Sirius (Harry’s godfather), informs him that Mr. Crouch had been working his whole life to become the Minister of Magic, only for his son to be caught with some of Voldemort’s supporters. Rather than helping his son, Mr. Crouch immediately sent him off to prison; he didn’t want anything to ruin his reputation. That just shows even more how much Mr. Crouch chooses for himself to withhold a very lawful prominence, and anything that hurt it, even his son, he would get rid of.
However, towards the end of the story, after Harry narrowly escaped from Voldemort, the imposter Professor Moody, who was Mr. Crouch’s son, reveals everything about the Truth Potion– how Mr. Crouch reluctantly helped his son escape from prison, put him under the Imperius curse to control him, and never let him leave home.