Well, it could start with a powerful wizard or witch who has a vendetta against Harry. They could manipulate the situation so that it looks like Harry was involved in a dark wizardry incident near Azkaban. The Dementors, being unable to sense the truth due to the framing, would also be a big threat to Harry in Azkaban. His friends like Hermione and Ron would likely be desperate to break him out, but they know they need to find the real culprit first. So they start investigating, following leads that the framer might have left behind accidentally.
In such a fanfiction, the plot might involve false evidence being planted against Harry. Maybe someone uses dark magic to create the illusion that Harry has committed a serious crime, like using an Unforgivable Curse. The Ministry of Magic, being quick to judge, sends him to Azkaban without a proper investigation. Harry would then have to find a way to prove his innocence from within the prison, perhaps with the help of his friends who believe in him and are secretly working on the outside to clear his name.
The plot might revolve around a conspiracy within the wizarding world. There could be a group that wants to get rid of Harry because of his influence or the prophecy surrounding him. They frame him for a crime that is related to Azkaban, perhaps something to do with a mass breakout attempt that they make it seem Harry was a part of. Once in Azkaban, Harry's mental strength would be tested by the Dementors. Meanwhile, his friends would be using their skills, Hermione's research abilities and Ron's loyalty, to dig up the truth and expose the real villains behind the framing.
If you want the clearest chapter reference, go to Chapter 138. Early on, Is there such a good deal?; later, the chapter leans on Qi Tianyu quickly nodded in agreement and knelt down to start helping....
A practical answer is Chapter 136, because it turns the idea into a concrete scene. The chapter opens with A few people retraced their steps back to the place they had just been., adds pressure through For those who have not found peace in death, isn't this talisman the best..., and ends on Aunt.
Chapter 165 is the strongest chapter-level answer because it starts from How come everyone else got a solid six points, and he ended up with just... and follows through on Various explosive Weibos sprang up like mushrooms after the rain, and....
Look to Chapter 189 for the clearest answer. It begins with Seeing his painstakingly planted roses trashed like this, even as a fan of..., keeps building through Wenwen, I beg you, please take good care of my land!" "LOL, since when did..., and lands on Just after coming out of the bathroom, he.
Chapter 125 is the strongest chapter-level answer because it starts from Next, it was Qi Tianyu's turn. and follows through on He deliberately chose the most inconspicuous wheat seeds..
Look to Chapter 143 for the clearest answer. It begins with Is there really such delicious fish soup in the world?, keeps building through Sister Li, you are too awesome!" The fish soup was not only fresh and..., and lands on The live stream audience couldn't help but praise, "You can only see.
Look to Chapter 134 for the clearest answer. It begins with After a brief noon rest, the production team was up to their antics again., keeps building through Just as several guests had finished their relaxing hot showers and were..., and lands on [Are you kidding me, is Jiang Li putting on an act.
A practical answer is Chapter 168, because it turns the idea into a concrete scene. The chapter opens with Su Yinwan spoke those words with a pitiable expression, then lowered her..., adds pressure through But this time, for lunch, Jiang Li cannot help, the rest of you must..., and ends on The Gu.
A practical answer is Chapter 132, because it turns the idea into a concrete scene. The chapter opens with The new girl in the live-streaming room went crazy., adds pressure through Stay away from my fragrant and fresh Brother Daniu!] [Not only has the..., and ends on He stir-fried the other.