Black Widow: Can you use your magic to determine how much time passed between the construction of S.H.I.E.L.D. H.Q. and Avengers Hall?
Loki: Of course, but why would I?
Black Widow: Because I'm closer to uncovering the power source we've both been looking for. If you help me now, I'll make sure you're there when I find it.
Loki: You have a deal, Widow-Woman. I trust you're not interesting enough to go back on your word...
Loki: Fury's spy building was constructed almost thirty years prior to any other building on this campus. What do you think it means?
Black Widow: I think this was a S.H.I.E.L.D. base before it was a school. I think S.H.I.E.L.D. was guarding a power source somewhere under our feet. I think he brought us here to be the new guard without us knowing.
Loki: And what do you think happened to the old guard?
Black Widow: I think we better find out before someone new is asking that about us...