Lying there in the darkness, she thought about what the Silver Arrow must look like from above, the way a bird would see it: puffing along through the snowy nighttime wilderness, small and determined, its headlight splitting the darkness. Its whistle sounded, and where before it had sounded huge and triumphant, now it sounded sad and a little lonely—the sound of something far from home that had come a long way and still had a long way to go.

The next day it was snowing harder, and the wind started to howl. It was a real blizzard. The Silver Arrow pounded through the storm, cutting through the wind, its cowcatcher sending snow fountaining off the track on both sides. Kate and Tom lit the woodstove in the library and wrapped themselves in blankets, and the porcupine sat in his armchair—which by this time was quilled beyond repair—and told them stories about his hair-raising standoffs with mountain lions and fishers, which were the only animals with the gumption to seriously take on a porcupine.

(A fisher was nothing like a fishing cat, the porcupine explained. Fishers were actually members of the weasel family, but much larger and more vicious than weasels. And they didn’t even eat fish! Another brilliant piece of naming by the humans.)

Kate went up to the engine to check on the Silver Arrow. The sun was setting, and they were crossing a frozen lake. The tracks ran right across the ice.

THIS MAKES ME NERVOUS

“Me too.” Kate peered out into the snowy twilight. “How thick is this ice?”

I DON’T KNOW

IT WAS A WARM WINTER. AND IT’S VERY LATE IN THE SEASON

“It had better be pretty thick.”

WHAT ARE YOU IMPLYING ABOUT MY WEIGHT

SORRY

I MAKE JOKES WHEN I’M NERVOUS

Kate took their speed up as far as she dared. The sooner they got off this ice, the better. The wind made snaky sidewinders of snow that slid across the frozen lake.

Crunch! Suddenly the whole train lurched and slowed for a second—then kept going.

“What was that?!”

I THINK THE ICE IS CRACKING

Oh no.

“That isn’t good.”

She gave the train all the speed she could, but a minute later it lurched again, harder this time.

I THINK WE JUST LOST THE CABOOSE!

This ice wasn’t going to hold them much longer. Kate sprinted back toward the library car. She met Tom and the porcupine in the corridor, coming the other way.

“The ice is cracking!” Kate said. “We’re losing cars!”

“We know!” Tom said.

Crunch! This time the train ground to a complete halt and everybody fell down in a heap. Kate banged her elbow on the floor hard enough to bruise. They could feel the engine struggling and straining to get moving again. The weight of the long train was dragging it back and down.

“Come on!” Tom shouted.

They raced each other forward to the engine.