I wasn't sure where to look. I wasn't sure how to look.
So I did what anyone self-conscious and startled would do: I tried to act cool. With the pack of giddy iPhoners all focusing their cameras in our direction, I gave nothing. I didn't ogle, I didn't double-take. I gave a wry smile and pressed on as though I had somewhere more interesting to be.
After all, I thought, this is New York - people there regularly see crazier things than a pair of tits.
One hates to think what people would have said if Moira had made her fashion statement in Middleborough, Massachusetts. The small town just outside Boston voted this week to fine anyone caught swearing in public.
Apparently, a town spokesperson says, youths have overrun Middleborough's parks and public places with their obscene foul-mouthed exchanges. Drop an S-bomb from now on and the police can drop you a $20 fine.
"Golly, gosh! That young lady's misplaced her top."
"Fiddlesticks, would you look at that."
Though one can appreciate the alarm caused by the profanest examples of youthful expression, you have to wonder whether a measly 20-buck fine will really act as an effective deterrent. Besides, foul language is subjective: one man's Whakatane is another man's breached bylaw.
And, above all, you'd have thought one man's offence is another's freedom of speech.
Meanwhile, nothing pleases, provokes or parts a crowd quite like a topless young woman with a point to prove.
Moira was the Moses of Manhattan, parting the sidewalk masses like a zipper on a puffer jacket. Though acting cool and in no way offended, I admittedly felt confronted.
And that, as it turned out, was the point.
A carefully key-worded Google search (kids, don't try this at home) revealed Moira to be a women's rights campaigner.
Since 1992, Moira will tell you, it has been perfectly legal for a woman to walk topless in New York in any place a man can do the same. Though she has occasionally been hassled, and was once mistakenly arrested, Moira is merely exercising her legal rights.
Avert your eyes or block your ears - one man's offence is another's freedom of expression.