BookGirlHPfanfic
Based off a theory my friend and I were discussing, don't know where we got it from but props to whoever it was :)
When Steve went back in time to return the stones, he stayed in the 1940s with Peggy, or did he? Could he leave one if his teammates behind? He has to at least try and bring her back.
Not a great description, sorry.
This is a clean fanfiction, you are all welcome ;)
All rights for characters and settings and all that jazz to Marvel. Only the plot is mine (don't take my plot, please!). The theory is also not mine, again, props to whoever came up with it.