It was a cool, crisp Wednesday in early May. That morning Nancy and Bess had flown from their hometown of River Heights to Jackson, Wyoming, where they had rented a car for the drive north to Yellowstone National Park.

"George would love this," Nancy commented as they passed a grove of aspen trees. "Too bad she couldn't come." George Fayne, Bess's cousin, had been forced to pass up the trip because of a long-planned visit to friends in Boston.

"Bet you can't wait to see Ned," Bess said. Nancy smiled broadly. Her boyfriend was one of a small group of Emerson College students who had been camping in Yellowstone for three weeks, studying the habits of the yellow-bellied marmot, a small, furry mammal common in the park.

"I do miss him. I just wish it hadn't taken an emergency to get us together."

"Who was it who got hurt again?" Bess asked.

"A graduate student named Brad Keeler," Nancy replied. "He was badly burned when a propane stove exploded the night before last, and Ned doesn't think it was an accident."

"Because all those marmot traps were stolen, right?" Bess said.

"Right. Over the last couple of weeks about four dozen traps have disappeared. It happened gradually, and no one realized they were missing because they were stored in several different places," Nancy explained. "But Brad finally noticed and was starting to look into it before that stove blew up in his face."

"How awful!" Bess exclaimed. "What was the study group doing with the traps, anyway?"

"They used them to catch the marmots last fall so they could attach transmitters to the animals," Nancy said. "That's how the Emerson people keep track of the marmots' movements."

"Neat," Bess said. "But why would anyone want the traps?"

"Ned thinks someone is planning to trap marmots with them and smuggle them out of the park, which is totally illegal," Nancy answered.