The heroes have fought their way through a swath of enemies in the dungeon, only to find themselves outside the final room—the one that contains a cult leader making vile sacrifices, and all of the cult’s treasure. Exhausted and out of resources, instead of pressing on, the adventurers decide to make camp and sleep for the night before facing the cult leader in the morning—right outside his inner sanctum.
What happens next?
In a realistic scenario, chances are good that the cult leader would finish his evil ritual, sacrifice the victims, then either use the escape route he had planned for when heroes are blocking the main door, or else sneak up on them while they are sleeping and kill them all. Usually there’s no believable reason why the cult leader wouldn’t notice the presence of the heroes, especially if he sends for any minions—only to discover that everyone else has been slaughtered.
In a dramatic scenario, the (well-rested) heroes break in just as the cult leader is about to complete his sacrifice. After a harrowing and exciting conflict, the heroes prevail and the cult leader is brought to justice, perhaps even taking the place of the sacrificial victim along the way! Sure this strains believability, but it would be anti-climactic for the leader to just win and escape with no confrontation.
So this brings us to roleplaying games. Published adventures have been written both ways. Commonly, map-based adventures have a more dramatic approach—for example, room 36 is where Phil is being tortured and is clinging to life. Whenever the players happen to get to room 36, Phil finally dies, but not before conveying some final last words to the players. This type of adventure does have the drawback of feeling like everything is in stasis until the PCs open the door. How long was Phil in room 36 waiting for the players to show up just so he could keel over and die? Probably for a long time. And what if the players somehow miss room 36? Is Phil alive (in case the PCs do decide to come back, days later), or dead, or in some sort of Schrodinger’s cat state of being both alive and dead?
Conversely, event-based adventures have a more realistic approach—for example, at 2:00 a riot breaks out, and at 4:00, the captain of the guard is murdered. The PCs are supposed to figure out who figure out who did the murdering, but what if the players become sidetracked? Say they get the false impression that Jimmy the Snitch, who mysteriously left town this morning, was behind the rioting. At 3:00, the PCs leave town to chase Jimmy the Snitch and completely miss out on the murder of the captain of the guard. In an event-based adventure, things keep happening whether the PCs witness it or not.
So which is a better approach? Perhaps a flexible, hybrid approach. Some game systems actually encourage the storyteller to make things up as they go and to not know all the answers. In such a game, if the players are intent on pursuing Jimmy the Snitch, maybe he did have something to do with the rioting. At the very least, the players seem to think that Jimmy the Snitch is more interesting than the riot, so perhaps he should get “promoted” to having a larger role in the story. Cast away your pre-existing plans and go where the players take you!
As a storyteller, it is important to remember that you are in fact telling a story, one in which the PCs are the main characters. It would be a poor story if they weren’t challenged, if they didn’t have a chance to stop the bad guy, if they missed vital clues, or if they spent all their time chasing red herrings. A good story must be both believable (realistic) and exciting (dramatic). If the players decide to rest outside the cult leader’s room, maybe the cult leader brings the fight to them. If they take too long getting to Phil, maybe he died, but left a cryptic clue written in his own blood. If they go chasing after Jimmy the Snitch, they might not find what they were looking for, but they might find something equally interesting and exciting.