Convert the current distance between groups into a Move bonus and immediately add it to the fugitive's running total, as if the fugitive has had a chance to run a short distance before the pursuers begin the chase. Now, run the chase exactly like a race, except that at the end of the turn, compare the pursuer's total Moves to the fugitive's total Moves. If the turn ends with the pursuer's total equal to or greater than the fugitive's total, the chase is over.
The chase is also over if the fugitive escapes. The default definition of "escape" is:
- The fugitive is 5 or more Moves ahead of the pursuer for three turns in a row; and,
- That distance is not getting any smaller.
The exception is if the fugitive is chased by something that never tires. For example, zombies can pursue relentlessly, if their commands allow it. Fortunately, they are usually commanded to attack creatures that enter an area, rather than ordered to attack and kill one opponent.
If the pursuer tires, of course, you can consider the fugitive to have escaped as well. This is just a specific instance of the obvious: if the pursuer can no longer pursue, the chase is over. This includes things like sealing a portal behind you, using a secret door unknown to the pursuer, or tricking the pursuer into taking the wrong branch at a corridor intersection.
Distractions can also help delay pursuit. Underworld & Wilderness Adventures mentions dropping food or treasure. A summoned monster might slow down the pursuer long enough for the fugitive to escape, even if the summoned monster is far too weak to win. Phantasmal Forces won't last if the caster is fleeing, but if the caster has a variant illusion spell that will last a short while after the end of concentration, other deceptions are possible.
The evasion rules are not really applicable to small scale chases, since they assume two opposed groups in the same wilderness hex. I'll discuss them in a separate post.