The bird was a white-bellied heron from a river in India, and she was about a yard tall and incredibly beautiful—her neck was long and curvy, and her feathers were a million fine shades of gray. She had a thin, rather tasteful silvery crest on the top of her head, and, as advertised, a pure-white belly.

“We used to be called great Indian herons, or imperial herons,” she said. “Come to think of it, I can’t think why we changed. Those both sound much better.”

Kate took the opportunity to ask her about something that had always bothered her, which was how herons could walk with knees that bent backward. It turned out that the heron’s knees worked exactly the same way human knees did, you just couldn’t see them because they were tucked up under her feathers. What looked like the heron’s knee was actually her ankle, and what looked like her lower leg was actually a long, skinny foot.

Kate found that explanation almost equally unsettling.

“I always thought if I ever went on an adventure with talking animals, it would be with bunnies and mice and that sort of thing,” Kate said. “I mean, no offense.”

“None taken,” said the porcupine (who was just a very grumpy North American porcupine from Michigan). “Though you’re lucky. Rabbits and mice are incredibly boring. All they talk about is vegetables and seeds.”

For dinner the heron and the cat both ate fish. The porcupine worked his way through a big heap of clover, then gnawed on a branch. The mamba didn’t eat at all.

“I swallowed a wild gerbil a few days ago,” he explained, “and I’m still digesting. Besides, the sight of a mamba feeding is too awe-inspiring for most animals to watch.”

“It’s probably the way you inject your prey with horrible venom,” the porcupine said, “that makes them suffocate in their own skin.”

“Oh, that’s only the beginning!” the mamba said. “Mamba venom also causes dizziness, nausea, difficulty swallowing, heart palpitations, and convulsions! Though it’s true, it’s usually the suffocation that does them in.”

“Well, I think it’s horrible.”

“You’re just jealous,” the snake said, “because you can’t shoot poison out of your teeth.”

At this point Kate excused herself to go to bed. She was as tired as she could ever remember being, and she wanted to find a Band-Aid for her shin. And she was worried about the polar bear. And the invader animals. And the train was still short of fuel. When all this started she’d thought it was just going to be one big thrill ride, and it kind of was, but adventures were turning out to be a lot of hard work, too. And kind of stressful.

Tom headed the other way, toward the back of the train.

“The sleeper car’s this way,” Kate said.