No matter how well you plan and prepare your adventure or campaign, something will always come along which will throw your plans straight into the trash. Your player characters fight when you plan for them to run away; or they run away from a combat scene. You set them up for their first skirmish with the scenario's Big Bad, and somehow they manage to kill him; or you roll for a wilderness encounter, and a tiny party of kobolds somehow make critical successes and wipe out the party on their very first adventure.

There are some useful game aids available which are intended to help you with the unexpected, including improvising when a game has to be put together from scratch for whatever reason, such as the scheduled Games Master suddenly being unavailable at the last minute.

Don't Stop

So the characters have just derailed the entire adventure, somehow. What should be your first act as Games Master?

Your first act should be to carry on as if they'd just slain one more insignificant random mook. Try not to let the Players cotton on to the fact that the whole scenario may have just been upended. Your favourite dead non-player character should not have fallen in vain.

Choose A Random Encounter

Don't roll for a random encounter. Pick one, either from your list of pre-generated random encounter groups or just have a number of mook characters turn up, spoiling for a fight. Turn the scene into a combat scene immediately, to take the Players' minds off what they've just done.

This is one time where my usual aversion to combat can be set aside. Combat scenes do have their uses - they allow the Players to focus their attention on the task at hand, and more to the point, they focus attention away from the more important matter at their feet.

"That's Odd"

If a combat scene out of nowhere does not sit well, call for immediate Perception checks in the area. Emphasise this check by saying "You notice something odd." Then allow them to ask questions, one at a time, and make a Perception check for each question.

Closed Questions

Closed questions have a "yes" or "no" answer. Examples: Is there something unusual here?, Does my character feel something is out of place?, Is this a trap? or Was this too easy?

To answer this, you can consult a Yes/No Oracle. Some supplements exist which are designed to replace a Games Master ... but nothing says that a Games Master can't use these supplements too.

An excellent instant oracle from an indie publisher, Ken Wickham, is called 100 Shades of Nay ... and Yea. This is a brilliant supplement to create random answers to closed questions, and they can catalyse the spinning off of the stalled adventure in another direction completely.

Open Questions

The six main open questions are Who?, What?, Where?, When?, How?, and Why?. Anyone can ask these questions at any time, including yourself as Games Master. But in the event of a completely derailed scenario, as Games Master you may need to come up with answers to these questions before the Players ask them.

The best time to prepare such emergency answers is before the story begins. The next best time is right at the point of catastrophe.

Keep Oracles Handy

Bring along oracle-style supplements to every single session, and consult them heavily, even during those scenarios where everything is happening exactly as planned. 

Pregame Prep: Contingencies

Prepare contingencies for your encounters. If your non-player characters manage to kill off the entire party of Adventurers, bring them into a scenario you devised beforehand, where they wake up in a white room, stripped of all but the clothes on their backs. Set them the task of finding where their armour, weapons, gear, cash, treasures, and magic items went to, whilst escaping from random prison guards. Set them the task of wondering where they are (a prison), and how they escaped apparently being killed (they'd been hit by trank darts or something).

At the very worst, this'll take up the rest of the game session, and give you time to bring them back on track in the next session.

If they've managed to kill someone you did not want them to even fight until the final battle, then have the Adventurers notice something odd about the corpse. It's wearing a mask, or it was shapechanged from some lesser minion to resemble the Big Bad. Or it could be their twin brother, giving the real Big Bad added incentive to want to kill the Adventurers, out of revenge.

The best way to avoid the Adventurers killing off the Big Bad too soon, however, has got to be to save the actual main Big Bad until the end. It's always an illusion, a deluded fool hypnotised into believing they were the Big Bad, or a hapless minion brainwashed into believing themselves into being the Big Bad.

And the best way to ensure the Adventurers do not get wiped out by a random encounter is not to subject them to wandering encounters - not, at least, the sort which result in mindless arcade violence for the sake of it. The job of wilderness and wandering encounters is never to kill the Adventurers anyway, but to give them opportunities to learn things about the Big Bad before the main story - assuming, as I have been all this time, that the point of the scenario has been a simple dungeon crawl.

Contingencies For Other Kinds Of Scenarios

Up to this point, the thrust of the post has been on improvising on scenarios which are straightforward dungeon crawls. The Big Bad is sitting in his dungeon, practically waiting for the Adventurers to come along and do battle to the death, or something. Basically, the plot of The Hidden Fortress, The Guns of Navarone, or That George Lucas Movie From 1977 ...

But there could be other types of scenarios, which are just as engaging.

Diplomacy and Intrigue

This is where Fioracitta, The Heart of Power comes into its own. But there are other game modules available which focus on intrigue, politcs, and treachery - such as Republic, by Mutant Chiron Games.

The biggest improvisation you can make, if your favourite mover and shaker is unexpectedly killed, is to reveal to the Adventurers that the person they just destroyed was not, in fact, the main villain, but rather working for someone (or someones) higher up the food chain.

Investigation

Your Players' Adventurers are Investigators, for want of a better term. It doesn't matter if the game is set in Mythic Babylon or M-Space: they are tracking down some miscreant, either to prevent a bigger crime from happening or to bring someone to justice for a crime already committed.

What happens if your Big Bad goes down in a hail of bullets at the end of the second act? Again, look to the "Diplomacy and Intrigue" solution above. If the story is set in the modern era, the Adventurers find a cell phone on the dead guy's person, with a video from someone else (holding a loved one in an undisclosed location), or they find incriminating texts and/or calls to and from somebody else: someone who is clearly, by the messages sent, calling the shots.

Head of The Snake

So the Adventurers have indeed cut off the head of the snake in the second act. What now?

Now, the game changes. Now, as Games Master, you lead the Adventurers through the consequences. The Big Bad has contingencies set up to avenge his death, by sending capable assassins after his killers; or a succession war starts up, as ambitious Lieutenants and henchmen start squabbling, and ultimately going to war over, their little piece of the Big Bad's empire of crime. This is a scenario which would work great in a police procedural game, an intrigue game, even a modern game of espionage or superheroes such as The Design Mechanism's forthcoming Destined or Department M.

Surprise!

The Adventurers could have killed the Big Bad, only to find the same person standing in the very next room, as though he had never even died. It had all been an illusion, or even some sort of strange spell or psionic mechanism to make them all think they'd just defeated the Big Bad - and, in fact, even their presence in the next room is also just another illusion.

One Last Thought

There will never be a perfect scenario, because the Players are so ingenious in figuring out who the shot callers are, and hitting them with everything they've got. If the little person in the corner of the room starts chanting and waving their arms about, chances are they're preparing some dangerous spell, so every character with a ranged weapon is going to aim right for the little guy with the pointy hat the minute they've done a Perception check in the room. They always assume that the mage is always going to be the master tactician, and they'll select that target accordingly.

If you find that your Players tend to think this way, and all you're doing is running arcade-style violence and dungeon crawling, the best arena in which to improvise is in the realm of scenarios where improvisation is practically a requirement: games where the objectives are dialogue, diplomacy, intrigue, investigation, and where surprises are practically expected - such as Raymond Chandler's famous solution to reader boredom, which involved a man bursting into the room, brandishing a gun. Just shoot back first, and ask questions afterwards. Just make sure there are clues in the dead guy's pockets, so you'll have someone else to ask questions to.

If your little improvisation - a discovery of strange foreign coins on the bad dead guy's person, or a letter from a third party, or a text or email to the Big Bad from the real shot caller - keeps the Adventurers on their toes, gets them to think that there was more to this than just a fight in a dark alley or some catacomb, then you'll be able to manage to turn what could have stalled your adventure in its tracks into a pause in the action, as it shifts in another direction. If your Players don't read this post, they could go along with your improv and not even see the join.

And if you make improv a part of all your stories, even the ones which are going smoothly and exactly according to your plan, then they may well never even realise how close they came to bringing your scanerio to an abrupt halt. Just carry on, and keep a straight face the whole time. You've got this.