Finally got to see this week's show, and from what I saw (and the clues already dropped), I would guess that the man in the iron mask is the real Jay Garrick and the Jay Garrick working with the team is actually the Earth 2 Hunter Zoloman aka Zoom. And, that the real plot was to "invent" Velocity-9, not "steal" Barry's speed.
Of course, all that could be a bunch of red herrings to make us think exactly that, too. But, this is TV and the season is building to a climax, so I'm thinking they're not going to be throwing that many more surprise twists into the story.