As someone who loves board games, I don't know why this hasn't occurred to me earlier. But if you're struggling to pull a plot together, it might be helpful to think of your story as a board game. Sure, it might be an unusual board game. The players might start and finish at different times and have wildly different moves, resources, motivations and goals. But as long as those goals are in conflict (which is essential to a story) then your characters are basically all playing a game. Start with Turn 1, Player 1. Become that player. What do you want? What moves are you going to make towards that? Then, become Player 2. What moves will they make? Are they aware of the other players yet? Repeat this for all players. Then move on to Turn 2. Which players are now aware of other players? Which players will have to adapt their moves based on what the other players have done? Which players are working together or against each other? Are any new players joining the game, or ha...