Spoilers ahead for Episode 13 of The Flash Season 5, "Goldfaced."
Team Flash has been bearing down on Cicada for quite a while, but it looks as though the tables will turn on them in the next week. Check out the trailer for "Cause and XS," which shows the Season 5 villain strike back at Team Flash in a big way.
Obviously these deaths may not be permanent, as Nora is trying to travel back in time and prevent the serial killer from killing various members of Team Flash. Unfortunately, it doesn't appear any amount of time travel she's engaging in is working. Will she be able to fix this mess on her own, or will she need someone else to clean up the mess she's made?
As far as how Cicada managed to get the drop on Team Flash, that's an entirely different question. Did Iris' visit in "Goldfaced" accidentally put him on their path, or is this another result of Nora bending the timeline? It seems like the latter is a strong possibility, especially given that bit with Barry warning his daughter about altering timelines. He's had that talk with her before, but obviously the lesson didn't take.
That's largely due to Nora's other mentor, Reverse Flash, who has been preaching to her that the timeline is malleable. Is he the reason Cicada is now tracking down members of Team Flash and killing them? He seemed to know exactly how to instruct Nora on arranging that meetup between Sherloque and his new crush, so it wouldn't be surprising to find out.
Whether or not this situation is Reverse Flash's doing or not, chances are he can bail Nora out of her mess. Unfortunately, that's going to put the speedster further in his pocket, and in a position to get a request granted she may not have done otherwise. It's not like The Flash viewers can blame her, of course. This is literally a life or death situation.
As for other unexplained mysteries that will probably be addressed in this episode, why isn't Barry going back in time? One would think if Iris was in danger of being killed by Cicada, he'd travel back and time and stop that regardless of the consequences. After all, he's not really one to preach the dangers of time travel to his daughter when they both literally went back in time together in the 100th episode and probably altered the timeline.