"Nobody Missed It at First"

"A Subway Named Möbius."
By A. J. Deutsch (1918-69).
First appearance: Astounding Science Fiction, December 1950.
Anthologized many times (see HERE).
Filmed in Argentina in 1996 (HERE).
Short story (15 pages).
Online at SFFAudio HERE (PDF with 2 illustrations) and HERE (PDF, no illos).

"At Park Street you get off the surface car underground and walk downward to get on the elevated. A few more complications and inversions and — maybe a fine research program?"

As far as we can tell, this is the author's only piece of fiction (how much editor John W. Campbell interfered with or contributed to the story isn't known); everything else Deutsch published was of a technical scientific nature. Even so, it's a classic and a favorite of anthologists worldwide.

When Number 86, the Cambridge-Dorchester subway train serving greater Boston, goes missing, it's three days before the realization sets in that, to say the least, something has gone horribly wrong:

By mid-afternoon, it was clear to the police that three hundred and fifty Bostonians, more or less, had been lost with the train.

(Click on image to enlarge.)

Principal characters:
~ Roger Tupelo, Harvard mathematician: "This is a very hard thing for anybody to under-stand, Mr. Whyte. I can see why you are puzzled. But it's the only explanation. The train has vanished, and the people on it. But the System is closed. Trains are conserved. It's some-where on the System!"
~ Kelvin Whyte, the General Manager of the line: "And I tell you, Dr. Tupelo, that train is not on the System! It is not! You can't overlook a seven-car train carrying four hundred passengers. The System has been combed."
~ Gallagher, the motorman on Number 86.
~ Dorkin, Number 86's conductor.

"But a network with infinite connectivity must have an infinite number of singularities. Can you imagine what the properties of that network could be?" After a long pause, Tupelo added: "I can't either."

Resources:
- A. J. Deutsch's solo SF outing has earned him entries on Wikipedia HERE, the SFE HERE, and MathFiction HERE (SPOILERS).

- If you're topologically minded (and who isn't these days?), Wikipedia has articles about the Möbius strip HERE and the Klein bottle HERE, both being copiously illustrated, thank good-ness.

- Number 86 can be analogized to the legendary Flying Dutchman, about which see HERE.

The bottom line: "Why did the chicken cross the Möbius strip? To get to the same side."
— Sheldon Cooper