The STAR Labs team believe that the reason Zoom chose to send Doctor Light through the breach to Earth One is because of the fact she's the doppelgänger of Linda Park, someone Barry knows and has had a relationship with, which would make him pause during their fight. This throws up a couple of questions. Firstly, how did Zoom know about this? Does this mean he has been keeping tabs on the events of Earth One, and in particular Barry? And does that mean he knows Barry Allen is the Flash? Also, and it's one raised within the episode, who else could come through that breach? Theoretically every character could have a doppelgänger somewhere in the multiverse, so are we going to be seeing various versions of Barry, Caitlin, Cisco et al? Can we have a scene of Zoom fighting both Barrys, where he says he's "seeing double...four Flashes!"?