Lady Sif (Jaimie Alexander) drops in from Asgard, but stricken with amnesia she can't remember why she has come to Earth.
Coulson's team dig up some online footage of Sif fighting a superhumanly strong individual and track him to a hospital, where they discover he's an undercover Kree called Vin-Tak (Warehouse 13's Eddie McClintock).
Yes, ladies and gentleman, a motherflippin' Kree! Things just got real, folks!
Skye doesn't even manage to keep her new superpowers a secret for an entire episode, as Vin-Tak and Lady Sif both have their own ideas of what should be done about her "Inhuman" powers (not that that label gets used this week).
Fitz's obvious complicity in trying to keep Skye's powers on the Q.T. drives a bit of a wedge between him and Simmons, but we get our best explanation yet - from Vin-Tak - of the origin of The Obelisk and the 'terragenesis' process that transformed Skye and Raina.
Meanwhile, as Bobbi and Hunter get closer, whatever shady goings-on Bobbie has with Mack get in the way, so Mack advises Bobbi to distance herself from Hunter. But he sees through this - with unexpected consequences.
Although Who You Really Are visited a number of countries (probably all portrayed by California), and referenced Asgard and Hala (home planet of the Kree) it actually felt quite a contained episode, focusing, as it did, primarily on Coulson's team - and their continuing internal frictions.
There are a lot of secrets coming to the surface and I sincerely hope they don't get dragged out. Let's keep up with the big reveals, then move on to the next plot point/twist/secret/conspiracy.
Clearly Mack and Bobbi are not working for Hydra - or any nefarious organisation - so let's get to the bottom of this mystery as soon as possible.
Oh, and bring back the Kree! But in the future don't let them bother hiding their true skin colour. I realise it's a probably a budgetary thing but Agents Of S.H.I.E.L.D. needs more blue-skinned aliens.