this. mods are the GMs and hold all the cards when it comes to plot. players can do plenty of things but if the mods don't give them results that mean something nothing will actually happen. if your game is a spooky mystery, leave clues that players can pick up on. if it's action, give them monsters to beat or a dungeon to explore. etc. or watch what players ARE doing and give them results based on that.

if they adopt a kitten send some zombies to try and eat it.