Cryptozoology

PREMISE: The player's Adepts are professional zoological explorers, out in the field searching for new and undiscovered species of plant and animal life (or it's a hobby, or they heard tales nearby of a fabled beast of legend, or it's the weekend before playoffs, whatever). The structure of this story is pretty simple: hunt down the mythic beast of obscure origin. This will involves lots of tracking, facing natural dangers (native tribes, poachers, trackless wastes, storms, etc.) and of course capturing the brute itself.
Generally speaking, finding the beast should be much of the story. Players will have to interview witnesses, investigate areas where the creature has been seen, talk with any scientific professionals about the creatures' habits or weaknesses. To make the story feel interesting, a good Storyteller will know to use NPC's to add foreboding, speaking of the creatures' dangerous capabilities and how others have tried and failed. 
THEME: Discovery and wonder, with a good dose of fear on the side, is the emotional recipe for this story. If the creature can only be found in a far and away place, having the characters travel through exotic locations like ruined temples and jungle vistas will add wonder.
CONFLICT: Aside from the dangerous monster out there somewhere, the player's Adepts might find themselves divided over the issue of whether or not to kill it. If the monster is some type of primate, and has human-like features, this may make it difficult for some to kill the creature. 
Also, a rival group may be attempting to get to the creature first. Maybe they're hunters looking for the same big kill, or maybe they created the monster and want to retrieve it. Either way, they will prove dangerous to the player's Adepts and must be dealt with.
RESOLUTION: The story culminates with capturing the beast and getting it out of there (or doing whatever it is your players have decided to do). Players should have a chance to enjoy their success, often in the form of praise and grants from people who have benefited from the creature's discovery (a museum, a zoo, an international biological research lab, etc.).