The story of The Borrowers ends so suddenly that even Kate, the little girl to whom Mrs. May tells the story, can't believe it:
"And that," said Mrs. May, laying down her crochet hook, "is really the end."
Kate stared at her. "Oh, it can't be," she gasped, "oh please… please…" (19.1-2)
Except. Wait. That's totally not the ending.
Of course not. As Mrs. May says, "stories never really end" (19.15). We can continue to tell the story of what happens to the Borrowers even if they were never seen again, which is exactly what Kate and Mrs. May do until the last page of the novel. They imagine the ending.
And they do a crazy awesome job, too.
In fact, the farther along in the story they go, the more real their imagined ending becomes. Kate and Mrs. May shift from speculation about what the borrowers would do to stating it as actual fact:
"[…] she'd bustle and fuss and cook and clean and make [their relations] wipe their feet when they came in."
"On what?" asked Kate.
"On a piece of moss, of course, laid down at the door."
"Were they all boys?" she asked, after a moment.
"Yes, Harpsichords and Clocks. And they'd spoil Arrietty dreadfully."
"What did they eat? Did they eat caterpillars, do you think?"
"Oh, goodness, child, of course they didn't. They had a wonderful life—all that Arrietty ever dreamed of." (20.18-24)
They start out talking about what the borrowers would do, if their story were to end. But as the conversation continues, they change tenses, to what the borrowers did do, as if the story had an ending all along. The conversation continues to switch back and forth between the two tenses, as the twosome builds up to the grand finale. They write the ending to the story right before our very eyes, so that when Kate says "so that is the end," Mrs. May says, "Yes […] it could be. Or the beginning" (20.3-4).
The story of the borrowers will never be over until we decide to stop telling the story of their adventures. And since we're still reading this book after half a century, we're betting it'll end sometime around… oh… never. Plus, there are oodles of sequels to devour, so get to cracking those book spines, Shmoopers.