The travelers stewed, caught between the trip they were sure they had completed and the sidewalk they could not reach, compelled to confront a question of ethics at, of all places, a subway turnstile.

But first they had to figure out, where had it fallen apart?

They had gotten off their subway train in Midtown Manhattan without incident. They followed a light at the eastern edge of the platform, rode up an escalator and passed through the turnstiles.

Then some turned left, up a small flight of stairs, past a Subway sandwich shop and a shoeshine parlor — both closed. Others went right, where a shuttered locksmith stood at the base of the stairs. This would seem cruel on the way back down.

For there it was, greeting all parties at street level: a pair of roll-down gates, slammed shut.

“I just feel trapped,” said Kate Lingley, 27, from Greenpoint, Brooklyn, weighing her next move. Then she noticed a fellow rider wandering past.