Arrow season 5 has managed to both create an interesting main storyline and thematic arc, and also deliver what is probably one of the best collections of individual character sub-plots in the show's run. Framing all of it is the big mystery of the deadly and methodical Prometheus.

Prometheus struck a particularly sadistic blow before Arrow took its midseason break; the villain tricked Oliver Quenn/Green Arrow into shooting down his former love Felicity Smoak's new boyfriend, Billy. That traumatic event is bound to have a serious effect on Felicity; she’s a character who has already been shown to have a dark side – one that’s almost as vicious as her light, chipper persona is amusing. As the Arrow EP teases, Ms. Smoak could be headed for a very drastic and unexpected character evolution.

As Arrow Executive Producer Marc Guggenheim teased to Collider, where Felicity goes in the second half of season 5 will be, "as with all things Arrow, it’s not initially what you think it is and it will ultimately relate to the overall season theme of legacy, but in this case something very specific to Felicity."

Fans are already buzzing about what kind of character turns Guggenheim could be referring to. Some popular theories are that Felicity will tire of seeing people around her get hurt, and will want to play a more active role as the third Black Canary (tapping that "legacy"). That theory is backed up with Guggenheim says the following:

"It’s the sum of a bunch of stuff, and Billy was sort of the final straw.... Felicity’s been living in this darker world for the last four-plus years now and one of the things we’re exploring is how much what Oliver and Diggle and Roy and Laurel have been doing as vigilantes affected her and affected her way of thinking about things." Competing theories include that she could follow in the footsteps of her father, the hacker known as The Calculator (Tom Amandes), and start taking a more winding moral path to cleaning up Star City (following her family and personal "legacy").