“Were you expecting to see the plesiosaur?” I asked.

“Nemo’s not a dino—” protested the first girl. Then she caught herself, and blinked, and said, “Um, yes. He’s ours.”

“I’m sorry. Maybe I got something in my ear when your friend here shoved me,” I said. “Did you just say the plesiosaur was yours?”

Dominic released the second girl, who rocked back and forth for a moment, torn between rushing to defend her prehistoric reptile and going to the aid of her much more modern, if not much more evolved, companion. In the end, the plesiosaur won, and she fled to stand next to the other girl, blocking “Nemo” from our deadly attentions.

“Yes,” snapped the first girl. “Nemo’s ours, and he’s never hurt anybody, and no one would believe you anyway, so you should just go. You hear me? Get out of here and go.”

“Since we weren’t doing anything but being near the reservoir when Nemo decided to pop his head out and start trying to bite my head off, I think you may be wrong about whether he’s ever hurt anybody,” I said. It was hard to sound gentle while I had their friend in an armlock. I leaned forward, murmuring in his ear, “Are you going to shove me again?”

“No, I swear,” he whimpered.

I let him go. He ran to his friends, cradling his arm and staring at me fearfully.

“You must have done something,” said the first girl. “Nemo wouldn’t hurt a fly.”

“Nemo has a fifteen-foot neck, which means he’s a pretty big boy,” I said. “Have you been dumping tadpoles in the reservoir to feed him?” They didn’t answer me. They didn’t need to. Their guilty expressions were answer enough. “There are a lot of frogs in there, so I’m going to wager that Nemo doesn’t eat frogs. They probably taste funny. So he ate all the fish in the reservoir—alas for the free-range goldfish population—and then he probably moved on to small mammals. There sure were a lot of missing pet fliers up at the mouth of the trail, did you notice?”

No missing kid fliers. Not yet. That was a small blessing. Things like Nemo were miracles of endurance and evolution, but they couldn’t be allowed to go around eating children.

The newcomers blanched. The second girl looked faintly sick. She must have been an animal lover, not just a plesiosaur fan.

The first girl leaned up to wrap her arms around Nemo’s head. The plesiosaur endured her affections surprisingly well for a prehistoric reptile. “I don’t care,” she said. “He’s not hurting anything, and we’re not going to let you hurt him.”

I sighed. “We’re not going to hurt him. But we might be able to help you save him. Or did you think you could keep him in the reservoir forever?”

The trio exchanged glances. Finally, the first girl asked, “Save him how?”

Girl #1’s name was Kim; girl #2 was Angie. The boy was Charlie. All three were students at the local community college, and had gone on an archaeological dig in Kansas the summer before. They’d fallen through a false floor in one of the caverns, and into a moist, warm chamber, where there’d been a nest mounded with leathery, football-sized eggs. Being scientists, they had naturally been fascinated, and being primates, they had naturally dealt with this fascination by stealing an egg from the edge of the nest.

“We thought it would be an old fossil with a remarkably well-preserved eggshell, but when we put it through the X-ray, we realized it was alive,” said Kim, stroking Nemo’s snout, as if to reassure herself that it was okay to tell us this. “So we smuggled it home in one of the specimen cases, and at the end of the summer, it hatched into Nemo here. My beautiful boy.”

The plesiosaur nuzzled her cheek. Kim laughed. Angie gave her a look that made it clear that Nemo wasn’t the only one who wanted to be nuzzling her. Kim didn’t notice. I felt like I was seeing their entire relationship in microcosm, and I didn’t want anything to do with it.

“When did you decide to put your pet in the reservoir?” I asked.

All three of them looked guilty. It was like I’d flipped a switch. Charlie spoke, saying, “It was my idea. Nemo was growing so fast, and we were afraid somebody was going to find him at the school. But nobody comes up to the reservoir.”

“Nobody except joggers, and teenagers, and homeless people looking for a place to camp, and birders, and whatever the ‘I like to look at butterflies’ equivalent of birders is . . .” I let my voice trail off, looking at the trio. They seemed to be grasping the seriousness of their situation.