Well, it depends on how the fanfic has developed their characters. If Beckett thinks Castle is cheating, she might try to investigate further to find out the truth. She's a smart and determined character. She could confront Castle directly, demanding an explanation. Or she might try to gather more evidence secretly. If it turns out he's not actually cheating but there's been some misunderstanding, she might still be a bit cautious and reserved around him for a while until she fully regains her trust in him.
In a fanfic scenario where Beckett thinks Castle is cheating, she might initially be in denial. But as evidence mounts, she could become angry and start to distance herself from him. This is because trust is a huge part of their relationship, and if she thinks he's violated that trust, it would be a big blow to their connection. Maybe she'd also start to question all the other aspects of their relationship, wondering if things were ever real between them or if she misread him all along.
In the fanfic, it could be that rumors start to spread around about Castle being unfaithful. Beckett might be influenced by these rumors, especially if they seem to come from reliable sources within the story. Also, if Castle has been acting strange lately, like being secretive about his whereabouts or his phone, that could make Beckett suspect that he's cheating.
She is probably angry and frustrated. She would demand Castle to explain why he thinks so and would be hurt that he doesn't trust her.
Maybe he saw Beckett spending a lot of time with another man without knowing it was for a case. Castle is a bit of a jealous type, and he might overreact to normal interactions.
He might react with jealousy. He could glare at Josh and then give Beckett a hurt look before storming off.
A Castle and Beckett baby fanfic could be about their journey into parenthood. It might explore how they adjust to having a baby in their lives. For example, Castle could be super excited and start writing new stories inspired by his new family experience, while Beckett might be a bit more cautious and protective.
He might be in denial at first. He could keep trying to convince himself that there's no way Beckett would leave him.
In a fanfic, their first kiss might occur during a more emotional moment. For example, Beckett could be sharing a deep, personal story from her past. Castle listens intently, and when she finishes, he just leans in. It's a kiss that's both a comfort and a new beginning, a way to show that he's there for her not just as a partner in crime - solving, but also as someone who cares deeply about her on an emotional level.
One possible scenario in this fanfic could be that Castle and Beckett race against time to find the kidnapped child. They might start by interviewing the family and friends of the child, looking for any leads. Maybe they discover that the kidnapper left a cryptic message that only Castle's writer - brain can decipher.
There could be. The Castle fandom is quite creative, and a pregnancy plot for Beckett is a popular trope in fanfiction. Some fanfics might focus on the romantic aspect of it, with Castle being over - the - moon and taking extra care of Beckett. Others might explore the more practical and challenging sides, such as Beckett still trying to solve cases while dealing with pregnancy symptoms.
There's also 'Beyond the Case'. This fanfic takes their story to new heights by adding some interesting plot twists outside of the normal case - solving scenarios. It shows how their relationship might develop in different, more challenging situations. It's a great read for fans who want something a bit more out of the ordinary.