One possible plot could be that Harry discovers some new evidence that proves Draco's innocence. Maybe there was a frame - up by some dark forces within the wizarding world. Harry, being the hero he is, feels compelled to act and uses his influence and skills to break Draco out of Azkaban. This could lead to them having to go on the run together, hiding from the authorities while they try to expose the real culprits.
It could be that there is a prophecy or some ancient magic at play which Harry discovers. This magic shows that Draco is crucial in the fight against a new and emerging dark threat. So, in order to save the wizarding world, Harry has to get Draco out of Azkaban. He does this by using his knowledge of secret passages and spells that he learned during his time at Hogwarts. Once Draco is out, they form an unlikely alliance and start preparing to face the new danger.
The plot could start with rumors reaching Harry that Draco is being unjustly treated in Azkaban. Harry, being the hero he is, decides to investigate. He uncovers a conspiracy within the Ministry of Magic that is trying to keep Draco locked up for political reasons. Harry then uses his connections, like his friendship with Neville who now has some influence in the Ministry, to get a hearing for Draco. During the hearing, Harry presents the evidence he has found, which includes magical artifacts that prove Draco's innocence, and Draco is finally released.
He might use the invisibility cloak. Harry could sneak into Azkaban unnoticed and then use magic to break Draco out of his cell. The cloak has served him well in the past, and it would be a simple yet effective way to get past the guards.
In this kind of fanfiction, it could happen in various ways. Maybe Hermione discovers some evidence that Draco was wrongly accused. For example, she might find that certain spells were cast on Draco to make him seem guilty when he actually wasn't. So she uses her intelligence and knowledge of magic to expose the truth and save him from Azkaban.
Well, perhaps in this fanfic, Harry notices Draco in a dangerous situation with Buckbeak. Maybe Draco was taunting Buckbeak and it got out of hand. Harry, being the brave one, steps in and uses his skills with magical creatures to calm Buckbeak down just in time to save Draco from getting seriously hurt.
One possible fanfiction could involve Harry finding out that Draco was wrongly imprisoned in Azkaban. Harry might use his influence and his skills as an Auror to dig deeper into Draco's case. He could discover evidence that clears Draco's name, like finding out that Draco was framed by some dark wizards who wanted to get rid of the Malfoy family's influence. Then, Harry would have to fight against the bureaucratic system of the Ministry of Magic to get Draco released.
One possibility is that Dumbledore discovers new evidence that clears Harry's name. Maybe there was a misused spell by the Ministry that made it seem like Harry was guilty. Dumbledore then uses his influence and magic to break Harry out of Azkaban and they begin to expose the real culprits behind the false accusations.
It could be that Draco is following orders from some dark forces. They see Ginny as a way to get to Harry, and Draco, being their follower, tries to target Ginny. He might think that by getting Ginny, he can gain more power or favor within those dark circles.
Well, Harry might save Daphne from Draco because Harry is always the hero type. He doesn't like Draco's pure - blood supremacist attitude. Daphne could be a target of Draco's cruel remarks or actions just because she might not fully conform to Draco's ideas. Harry, being the defender of the underdog in many cases, steps in. Also, it could be that the plot of the fanfiction is building a new alliance or relationship web, and Harry saving Daphne is a key part of that, leading to new story developments.
It could be part of a plot where Draco is given an assignment by someone in the wizarding world to save Harry from the Dursleys. He initially does it for self - serving reasons like getting in good with certain powerful wizards who are concerned about Harry's well - being. But during the process, he actually starts to care about Harry.
In the fanfiction, it could be that Daphne has some unique magical ability that she uses to protect Harry in Azkaban. They might encounter other inmates who are actually innocent too and together they start a mini - revolution against the unjust system of Azkaban. Harry, with his experience of facing Voldemort, might lead the way in finding a way out of the prison.