avengers_search | Omega!Peggy role reversal

Lately I've been thinking about an ABO fic I started reading maybe a year ago, but never finished. I remember it had Peggy unexpectedly going into heat during the war, and Steve was the only one around. It was my first encounter with ABO, so I read far enough for things to start getting frisky and then backed out in a hurry going "WTF was that and how do I unsee it?" (Ah, those were the days.) Anyway, I *think* Peggy was an omega but had been hiding it, and alpha!Steve was making an effort to act submissively to put her at ease? But I'm not sure, because I knew nothing about ABO dynamics at the time, so it was pretty confusing.

I guess I'm less interested in finding that specific fic than in the dynamic I thought I saw--Peggy hiding her omega status, and Steve (or heck, it could be anyone) finding out but accepting the role-reversal. Sort of trans-alpha Peggy, almost, maybe?