Barry Allen (played by Grant Gustin) and Iris West (Candice Patton) discovered that the Mystery Girl was, in fact, their speedster daughter from the future, Nora Allen (Jessica Parker Kennedy).
She then told them she had time-travelled from the future and revealed she had made a “big mistake”.
The premiere of season five will reportedly be titled Nora.
Nora had come from the future to warn them of something she had done, and it looks like Team Flash are going to find out what her big mistake was in the very first episode of season five.
Fans still don’t know what that mistake will be, but recent set photos hint at Barry being involved in another time-travelling scene.
One theory could be that Barry will have to go back in time to stop Nora’s mistake from causing havoc.
The second episode of The Flash’s fifth season is titled Blocked, which is more enigmatic.
The title could be a reference to Barry’s efforts to help Nora being blocked by something or someone.
Could he be about to encounter another speedster whose intentions aren’t as noble as Barry’s?
The word blocked could also be a reference to Barry losing his speed, which fans have seen before in the show.
In any case, Barry has certainly learned his lessons from his experiences with time travel and is easily the best person to help Nora fix her problem.
“I don’t want to spoil too much of it, obviously,” The Flash star Grant Gustin said last month.
“I don’t know too much either. What I could presume is that we’re going to see… I mean, [Nora is] trapped in our time.
“I think, we’re probably going to see Barry trying to help her figure out a way to get back to her time.”
He added: “And see Barry and Iris interacting with an adult version of their child. I mean, it’s going to be really cool.
“We’re gonna see a new speedster, so. Get ready,” teased Gustin.
Whatever happens, fans will be looking forward to seeing Barry and his family do a lot of very fast running in the upcoming season.