On their way back to Ashley's house, they passed the Chickenshack High School. In front of the football field, a billboard showed a cartoon cat and bright letters reading "Home of the Chickenshack Cougars." As they drove past, Ashley did a double take. "What the heck?" she exclaimed.

"What is it?" asked Neil. Then he saw it, too: in the middle of the field was a round bluish-black spaceship, about the diameter of two school buses placed end to end. As a surreal touch, green racing stripes were painted on the sides. "Please tell me that's a Halloween decoration."

"Oh, no," said Ashley as she pulled the car over. She turned around in her seat and started rummaging in the back.

"What are you looking for?"

"This." She showed Neil the copy of To Serve Man. "If I remember right, just after the recipe for French toast, there's a picture…" she trailed off.

"French toast?" Neil asked, still staring at the spaceship.

"Apparently they taste better to aliens than Spaniards or Belgians. Oh, boy. Here it is." She showed him the picture in the book; it was a replica of what they saw on the fifty-yard line.

"What kind of ship is it?"

"Remember how Mimics will tell the truth if the last statement they hear is true, and lie if it's a lie?"

"How could I forget?"

"There's another group of aliens called Contrarians. Contrarians are the opposite of Mimics. If they hear someone tell the truth, they'll lie. If they hear someone lie, they'll tell the truth."

"You mean..."

"That's right. We've got a whole new group of aliens on our hands, and they've just invaded the high school." Ashley looked at her watch. "Luckily, it's after three, so there shouldn't have been too many people inside. Shall we check it out?"

"Guess we'd better."

They entered the building. Immediately they saw a group of three nervous-looking teenage boys in Halloween costumes. Neil was suspicious. "All right, boys. Tell me the truth. Are you aliens?"

"Yeah," said the first boy, trying to look tough. He was dressed as a pirate, so it didn't work very well. "I'm a Contrarian."

Neil looked hard at the second boy, who had a fake mohawk. "What about you?" he demanded. "Are you a Contrarian too?"

The boy stood silent, eyes wide open, until the pirate nudged him. "Um, yes, yeah, sure."

"Me too," said the third boy, who was wearing a white apron and a chef's hat.

"Neil," said Ashley quietly. "Up until this afternoon, I know these boys were human. But now..."

"Yes?"

"Only one of them is lying."

Which one isn't an alien?