When I last checked in my players were chasing a group of thieves known as the Dead Rats through the Neverwinter underground. The Dead Rats thieves, hired by a group called The Nashers, set out to steal a large portion of Neverwinter's treasury.
By draining the treasury, The Nashers hoped Lord Neverember would now be unable to pay the Mintarn Mercenaries he had hired, leaving the city open for the taking.
As the Mintarn hires were closing in (mid-robbery), the group decided it would be best to follow the Dead Rats, seeing as being found in the middle of a robbery scene would not be an ideal spot to encounter guards.
"What happened?" You might ask. Nothing. We did not play. The next stage of the mission calls very specifically for five players, and two were unable to make it.
Not knowing what to do, as a DM I found myself in a bit of a dilemma. I had no unique adventures planned, or with me. I was set up to play the next session, and if we slogged on missing two people (or had two players play two PCs), the game would not feel right. We would be bogged down with details. I also felt that to continue would be too much story exposition to explain the next time around.
I reached into my bag where I carry all of my guides and thought of what to do. We didn't have access to a printer so that I couldn't print out pre-gen character sheets. Instead, I handed everyone a piece of blank ruled paper and gave them stats based on NPCs in the back of the Monster Manual.
A Knight, an Assassin, and a Mage. Nice rounded 3-player team, right?
Next, I pulled out my trusty Sword's Coast Adventuring Guide and flipped to Luskan, a city just north of Neverwinter and where the Dead Rats reside.
Now, I had an entire backstory planned, in plot detail, for who was involved in the robbery, where they came from and why the Dead Rats were the group chosen (beyond that it is F.R. cannon that the Nashers and Dead Rats have worked together before). I decided I would place each player on a different aspect of the backstory... and just sort of run with it. I told my story and adjusted the minute details for what the players chose to do.
It worked surprisingly well. I used standard DCs for all ability and saving throw rolls. I ran monsters 100% from the Monster Manual, and walked them through the story.
Here's the best part: the players didn't know that. They had no clue they were running characters that would play a part in the Neverwinter robbery until the robbery happened. And? We ended the game just as the wall blew up, and the other five characters stepped through.
Sometimes improvised games are the best, but this one worked out.