The case of the lone wolf began last September 30, and it isn't closed yet... Seems a hunter just south of Yellowstone National Park came upon a prowling animal. Thinking the animal was a coyote — and so, fair game — he shot it. But then he took another look. Up close, the animal looked an awful lot like a gray wolf — an animal protected from hunting by the Endangered Species Act.

The hunter turned himself in. But the rangers were more interested in knowing where this "wolf" came from than in prosecuting the remorseful hunter. The reason? Gray wolves haven't been seen anywhere near Yellowstone since the 1920s, when U.S. rangers hunted the species to the point of near extinction. If the killed animal was indeed a gray wolf, where on earth did it come from?

To track down the dead animal's origin, the rangers called on the wildlife detectives. Right away, Steven Fain, the scientist in charge of the case, figured there were only three possibilities:

The animal could be a pet — half-wolf, half-dog — turned loose by a careless owner. (Wolves and dogs are so closely related that they can interbreed.)

The animal could be a Canadian gray wolf that migrated south from upper Montana.

Or, most intriguing of all, the animal could be a "descendant" of the old Yellowstone gray wolf population. "If so," says Fain, "I'd just be astounded."

So would many nearby ranchers. Right now, they're howling mad about a plan by the U.S. Park Service to reintroduce mating pairs of gray wolves to the area. They fear the wolves will kill their livestock. If the wolves already live in the area, the ranchers could argue that the reintroduction plan is unnecessary.

Fain had to pick his way carefully through the evidence in this controversial case. A molecular biologist, he decided to look directly at some molecules — samples of the dead animal's DNA.

DNA is the molecule with all the instructions that make you a unique individual. But you do share certain characteristics — and DNA — with your relatives and with other members of your species.

Same goes for wolves. By comparing the dead animal's DNA with that of other animals, Fain might be able to determine if it is indeed a wolf or a member of some other species.

Crime Lab

First Fain compared the animal's DNA to DNA from coyotes and seven different dog breeds. No match. "So we're calling it a wolf," he says.

But which wolf population did it come from? To find out, Fain compared the DNA to DNA from wolves in Montana, Alaska, and Minnesota. Again there were no matches.

Taking another tack on the investigation, Fain's partner, Bonnie Yeats, compared the wolf's skull with skulls from other wolf populations. Once more, there were no matches. The Yellowstone animal belongs to none of the nearby wolf populations.

Yet it still appears to be a wolf. Could it possibly be a descendant of the original Yellowstone wolves? And how do you prove it when you have no known living members of that population to test?

Fain has one hope. He's collecting all the vintage wolf skulls and hides he can get his hands on — from hunters, scientists, and museums. If he manages to get enough undegraded DNA from these samples, he'll be able to run his analysis.

And if the DNA matches closely enough, the evidence will point to an incredible story: a population of wolves thought to be wiped out from the wilderness, actually surviving unnoticed for 70 years. Then the new mystery will be: Where are they all hiding?

This article originally appeared in Scholastic's Science World Magazine.