A possible plot could be centered around a new threat in Gotham. Batman and Nightwing both have different plans to deal with it. Batman's plan is more secretive and involves a lot of solo work, while Nightwing wants to involve the public and work as a team. Their conflicting plans cause them to oppose each other.
Another plot could involve a difference in ideology. Batman might believe in a more strict and unforgiving approach to crime - fighting, while Nightwing has a more lenient and rehabilitative view. This could lead to a clash between them, both physically and in terms of their beliefs.
One idea could be a misunderstanding. Maybe a villain manipulates information to make Batman think Nightwing has turned bad. So, Batman starts to hunt Nightwing, while Nightwing is confused and has to prove his innocence.
One idea could be a story where Nightwing has to take over Batman's duties temporarily in Gotham. He faces a new villain who is specifically targeting Batman's absence and Nightwing has to prove himself not just as a replacement, but as a hero in his own right.
A plot idea could be that Nightwing is injured while saving a group of hostages. Batman then has to deal with the criminals who were holding the hostages as well as take care of Nightwing. The story could explore Batman's feelings of guilt for not being there in time to prevent Nightwing's injury.
A great plot could involve Nightwing training a new generation of heroes in the 'Batman Beyond' universe. He could share his old - school combat techniques with the more tech - reliant heroes, leading to some interesting clashes and growth. For example, he might have a hard time getting used to the new gadgets while the younger heroes struggle with his more hands - on combat style. And together they have to face a villain who is exploiting their differences.
One idea could be a misunderstanding. Maybe some false information makes Batman think Wonder Woman has been compromised and he has to stop her. Another could be a competition for a powerful, mysterious artifact that they both believe they should safeguard. And a third idea could be a mind - control situation where Wonder Woman is being controlled by an enemy and Batman has to fight her to break the control.
One idea could be that Batman discovers a hidden agenda within the Justice League that he believes endangers the world, so he decides to oppose them. For example, he might find out that a new technology the League is using has unforeseen and dangerous side effects.
One idea could be that Nightwing is captured by a powerful new villain in Gotham. Batman has to use all his detective skills to find Nightwing's location. Then, in a intense showdown, he battles the villain's minions and finally rescues Nightwing. Maybe Nightwing was being held in an abandoned warehouse on the outskirts of the city.
One idea could be a story where Batman has to carry an injured Nightwing out of a dangerous situation, like a collapsing building during a fight with a powerful villain. It could show Batman's concern and determination to save his protege.
One idea could be that Batman suspects Superwoman of being controlled by some unknown force. So, he starts to investigate her in secret. Superwoman, on the other hand, notices Batman's strange behavior and thinks he's up to no good. This leads to a series of confrontations between them.
A great plot could involve a race against time. A powerful new super - weapon is about to be unleashed in Gotham and New York simultaneously. Spiderman and Batman have to put aside their differences and work together to stop it. Along the way, they learn from each other's fighting styles and detective skills.
In a fanfiction, perhaps a powerful tech mogul has created a dangerous new form of artificial intelligence that threatens both Detroit (Robocop's city) and Gotham. Robocop and Batman cross paths while investigating the same lead. Robocop is intrigued by Batman's ability to operate without the high - tech enhancements he has. Batman, on the other hand, is interested in Robocop's in - built weaponry and combat capabilities. They combine their resources and fight the AI - controlled robots and henchmen.