Characters encountering some sort of horrible monster that they (wisely) choose to run away from has become fairly common in our campaign, and I think fits the inspirational material quite nicely. Of course once the players choose to have their characters run away from something we're left with determining whether they are successful, or if one or more of the group aren't fast enough to get away.
Referring to the basic rules it's a simple mater of comparing movement rates. If you're faster than the monsters you get away, and if you're slower you get caught. This is bad news for characters with heavy armour and lots of equipment, or if the monsters aren't overly slow moving. There might be some strategy around dropping food or treasure (or retainers) to try and distract your pursuer, but overall I think this is lacking a bit of suspense in the actual "chase" part of the scenario.
Now I think it's fairly obvious that a slow moving character isn't going to outrun a fast pursuer in a straight foot race in open terrain - but the "running from the monster" situation usually isn't conducted like that… or if it is the players will soon learn why it shouldn't be. Rather the players will have some sort of head start which may get shorter or longer depending on relative movement rates, and subject to:
- rolling to see if their character can get past an obstacle (eg. climbing out a window) or move quickly across hazardous terrain (eg. running across the rooftop)
- using resources to try and delay their pursuer (dropping food, treasure, caltrops, crazy old prospectors)
- choosing to go through doors, windows, around corners, under fences or otherwise taking a path that will delay their pursuer or end the chase
I've found that a good head start can actually be more exciting than close pursuit from an enemy. Letting the players choose when to start running as a monster breaks through the bars of it's cage or deals with some NPC before turning it's attention on the PCs always seems to create a suitably tense and exciting atmosphere.
In general I've been fairly happy with the chases in our games so far. Next time I'm going to make sure we're a bit more clear on the relative speed of the characters though, and which ones are being slowed down the most by their equipment.