In order to flee from a monster, you must pass an Evade check. If you succeed, the combat ends. However, you are still in the same space as the monster. In order to leave that space without fighting the monster, you must pass a second Evade check on your next turn. So, in order to escape from a monster without killing it, you must pass two Evade checks in a row. Is that correct? If so, it seems like fleeing is rarely a sensible strategy unless you truly have no chance of beating the monster in combat.
Also, if you flee from a monster, but fail the second Evade check on your next turn, do you need to make a second Horror check against the monster?