Okay so I have an idea, but i dont know where to go with it.
A semi-dystopian future/alternate reality where a disease like the bubonic plauge infects most of the world. There are a few left, but they're few and far between. The story centers around a young plague doctor named Nikolaia, and his girlfriend Jess, who live in what used to be Whales. Jess has a very weak immune system, and catches the virus. She is slowly and painfully dying, but Niko wont let her go out like this. They go on an epic adventure to find the cure, which has only been discovered in what used to be Russia, and they have to go by foot. They meet other doctors and miscelanious people along the way, some joining them. I don't know where to go from them
Come up with subplots for your doctors and miscellaneous side characters. You don't want your story to veer off too much from the main overarching plot, but you do want to make all of your characters meaningful. Plus, using your imagination to dream up subplots, character arcs, and any cool scenes or interactions you want your characters to share will help you expand and flesh out your story.
I'm assuming the end is when they find the cure, right? Well, work out what steps need to occur in the course of there adventure to get from Point A to Point B. What kinds of dangers do they face along the way? What kinds of enemies and antagonists? How does Niko take precautions to avoid contracting this disease himself? What are each of the side characters' reasons for joining? Are they, too, sick, or has one of them lost a loved one to this horrible disease and now wants to help make sure no one else dies?
Just sort of dig deep into your characters and start brainstorming things that could happen. Imagine, imagine, imagine! Write down ideas for cool scenes. Emotional scenes, dramatic scenes, high-tension scenes.
I know it's not super specific advice, but with writing you really just have to find the right way to spark your imagination.
Thank you so much! This helps
