Spoilers ahead for Episode 5 of Arrow Season 6, "Reversal."
The vigilante scene in Star City is quite different in Season 6 now that Oliver Queen has stepped down from his role as the Green Arrow and passed the hood on to John Diggle. While that particular arrangement is bound to fall through sooner or later thanks to Oliver's instincts and Diggle's dangerous method of stabilizing his terrible injury, Team Arrow is doing pretty well for themselves at the moment. Unfortunately, "Reversal" dealt Team Arrow a big blow when two big villains joined forces. Black Siren and Cayden James (formerly of Helix) partnered up in a mission that took them behind a well-secured firewall in a win that could result in a lot of collateral damage.
"Reversal" actually established that the partnership between Cayden James (Michael Emerson) and Black Siren goes back a number of months, as James is evidently responsible for saving Black Siren from almost certain death on Lian Yu after Prometheus blew it up in the Season 5 finale. Prior to "Reversal," Black Siren and Cayden James didn't seem like the two baddies most likely to team up. After all, Cayden James was introduced (although not in person) as a master computer hacker with his eye on changing establishments, and Black Siren didn't seem to have much of a grand plan beyond destruction. As it turns out, James needed Black Siren to do some murderous leg work in furthering his cause.
Black Siren was on the streets of Star City, killing a few people who seemed absolutely ordinary and had no connection to her. We eventually found out that Black Siren was really killing them to steal their fingerprints to access their secure cyber networks, all so Cayden James could kick off the next stage of his plan to do a lot of damage to a lot of innocent people.
At first, it seemed like James might have been a mustache-twirling victim who wanted nothing more than to watch the world burn. After all, the good guys believed for a while that his end game was the destruction of the internet. James explained to Black Siren at the end of the episode that he simply wanted to get Felicity's attention so that she would cyber-investigate. In doing so, she got her cyber-fingerprints all over a firewall that James is going to use in his real grand plan to cause damage. If James is successful in his goal, Felicity could go down for his crimes.
All things considered, Black Siren and Cayden James made for a formidable pair. While he was obviously the smarter of the two with a plan that seems to be ten steps ahead of Team Arrow, he still needed somebody to do the dirty work on the streets. Black Siren specializes in doing dirty work. The episode ended on an ominous note, with both baddies still working in the shadows and bound to come back yet again. James seems to have a lot more in common with the Thinker on The Flash than Black Siren, but perhaps that will make their work together all the more interesting.
This probably wasn't the only villainous team-up we'll see in Season 6, so be sure to stay tuned. You can catch new episodes of Arrow on Thursdays at 9 p.m. ET on The CW. The big four-show crossover is coming up that will team the heroes of Arrow up with the good guys of The Flash, Legends of Tomorrow, and Supergirl, so there's a lot to look forward to. Don't forget to take a look at our fall TV guide as well.