One afternoon, a young adventurer named Piper burst through his door, trailing the scent of rain and distant mountains. She slapped a crumpled map onto the counter.

He led her to the back room, where a shelf held a single, unassuming timepiece. Its face was engraved with a hobbit-hole door, round and green. The hands were made of two tiny, hairy feet.

“This is the There and Back Again ,” he said. “Wind it once. For exactly the runtime of a hobbit’s unexpected journey—no more, no less.”

“How long is that?” Piper asked.

Piper took the watch, crossed the pass in ten minutes, and spent the remaining two eating a stolen scone on the troll’s snoring belly. She returned the watch the next day, slightly singed, slightly smug.

“I need a hobbit runtime,” she said, breathless. “The old pass is guarded by a troll who only falls asleep for eleven minutes every century. The journey to the pass takes twelve.”