That was my first thought. Then I thought it was too obvious. Then I started considering all kinds of unlikely people - like Ward or the gal in charge of the government group they've been reluctantly working with.
Well I am basing it on the fact that I am sure it wasn't Andrew lying in that pool of blood and was blown up.
And Strucker's kid looked scared instead of someone who came out on top in a fight.
(Unless there was a last minute rescue that we will see next week).
It's possible he doesn't even know - like the old days when Banner became the Hulk and had no idea what the Hulk was up to.
First I thought it might have been Jemma, but that thing was around while she was still on that other planet.