Milo was a monorail, sleek and silver, with a hum that you could feel in your back teeth. Every night he ran the high track through Neon City, where the signs blazed pink and blue and the towers reached up like fingers trying to touch the moon. Hum, hum, hum — that was Milo, steady and sure.
Tonight Milo had one passenger. A small robot named Cog climbed aboard at the starting platform, clutching a paper ticket in his pincer hand. Cog had three wobbly gears on his back and a little screen on his chest that blinked the time. "Topmost Station," said Cog, in a voice like a tin cup rolling down stairs. "Before the midnight chime. My spare parts will be waiting." Milo gave a smooth, agreeable hum. Hum, hum, hum. He knew the way. The high track curved between the towers, and Cog pressed his round head to the window. A neon fish sign flashed green, then orange, then green again. A window-washing robot on the forty-second floor waved one soapy arm. Cog waved back, and two of his gears went clickety-click with excitement.
Then Milo rounded the Spiral Bend — and stopped. There, wedged sideways across the rails, was an enormous fallen billboard. It had advertised ZORKO'S EXTRA-FIZZY LIFTING JUICE, and now it was jammed tight as a cork, its edges scraping both sides of the track. Too wide to push through. Too tall to nose over. Milo's headlights lit up the shiny silver letters and went no further. Cog's chest-screen blinked. Eleven fifty-one. Nine minutes to midnight.
Milo couldn't go back — Cog would miss the chime. He couldn't go over — the sign was taller than his nose. Milo sat very still for exactly four seconds. His wheels hummed against the rail. And then he remembered. Hum, hum, hum. Just ahead of the billboard, hidden behind a relay box covered in old stickers, was the split-switch junction. A secondary loop. It curled down, under the city, through the underground glass tunnel where the fish tanks were. Nobody used that loop at night. Nobody except Milo, right now. Milo activated the switch. CLUNK — a deep, satisfying sound, like a giant key turning in a giant lock. The track shifted. Milo angled his nose downward and slid beneath the street.
The tunnel was dark and cold and curved like the inside of a seashell. Then the glass walls lit up — because on the other side of the glass were the city's famous underground fish tanks, enormous and glowing blue-green in the dark. A fish the size of a school bus drifted past, one enormous golden eye blinking slowly. Cog's face was flat against the window. His gears had gone completely silent. His little screen had stopped blinking the time. He had forgotten, for one whole minute, to worry about anything. Then — WHOOSH. They burst back up through the tunnel on the far side of the billboard, rails sparkling, cold air rushing in through Milo's vents. Topmost Station glittered ahead, and on the platform sat one small neat box with COG written on the label in large red letters. The midnight chime rang out across the city. One. Two. Twelve long, deep, golden notes. Cog collected his box and turned back to wave, his wobbly gears spinning properly now, all three of them, quick and quiet and right. Milo gave one last hum. Hum, hum, hum.
He glided back down the long track to the depot, slower now, the city going quiet around him. His engine cooled in small ticking clicks, one by one by one. His lights dimmed — the front lights first, then the side lights, then the little amber one above the door. Milo settled onto the track, still and silver, the city dark and soft above him.
