“Arrow” Season 4, episode 17 saw Oliver Queen (Stephen Amell) face a villain that previously appeared on “The Flash.” The CW

Just when Felicity Smoak (Emily Bett Rickards) thought she could escape the team on “Arrow,” a villain from her past returns and forces her to fall in with heroes once again on the CW drama. “The Walking Dead” star Emily Kinney guest stars as a baddie, previously introduced on the network's “The Flash,” to demand some precious technology.

In Season 1, episode 18 of “The Flash” Felicity showed up in Central City to help the speedster take on a villain named Brie Larvan (Kinney). Larvan was a mad scientist working for Mercury Labs that went after the former co-workers that scorned her with her hive of robotic bees. In “Arrow” Season 4, episode 17, titled “Beacon of Hope,” she was back for another round with the super hacker.

The episode opens with Oliver (Stephen Amell) and the team training hard in the wake of his recent breakup with Felicity. When everyone but him tapped out for the day, Thea (Willa Holland) mentions that her boyfriend, Alex (Parker Young), is in need of job. Although it’s awkward, Laurel (Katie Cassidy) suggests asking Felicity to get him a job at Palmer Technologies.

Elsewhere, Felicity is having a meeting with Curtis Holt (Echo Kellum) about the viability of marketing the implant he created that gave her the ability to walk again. Sadly, one small implant costs too much money for it to be mass produced and it seems that the only prototype the company can afford to make is already inside her spine. That ends up being extra bad news when Larvan sends an employee to a board meeting only to let a swarm of her bees murder him from the inside. She enters, makes it clear both that she’s in control of the building and that she’s capable of coming up with a lot of bee puns. She demands Felicity’s implant and when she, her mother Donna (Charlotte Ross) and Thea look out the window, they see Larvan's swarm of thousands surrounding the building.

The news covers the event and Curtis, who has gone home for the day with a 105 fever, leaps out of his bed and rushes to Oliver’s apartment to get help. While he’s there, he accidentally discovers the bunker where Oliver, Diggle (David Ramsey), Laurel and Captain Lance (Paul Blackthorne) are suiting up to launch a rescue mission. After passing out with excitement and fever symptoms, Curtis wakes up and gets the basic speech one gets when Oliver's secret identity is discovered. He uses the supercomputer that Felicity built to prove he can hack the perimeter of bees to let the team in. Reluctantly, Oliver agrees to let him be a temporary part of the team.

What’s left of the group reaches the back door of the Palmer Tech building just as the trio inside, having been given directions by Curtis via a hacked bee-bot, come out. Unfortunately, the plan doesn't work smoothly and Larvan reveals a new trick with her mechanical minions. They form a scary-looking Bee Man, Transformers-style, that attacks and subdues Oliver with a sting, putting the hero out of commission and officially making Plan A a failure.

"Arrow" Season 4, episode 17 featured special guest star Emily Kinney from "The Walking Dead," pictured here as the villain Brie Larvan. The CW

Back at the bunker, the bee is inside Oliver and Curtis realizes that it’s somehow replicating itself inside of him. As a result, he’s on his way to having a swarm explode out of him in a confined space with the rest of the team. Curtis accidentally finds his way to a solution to stop the bees that allows Black Canary to use her weird sonic cry weapon that’s usually otherwise worthless. It works and the bees stop replicating, but they’re still inside of Oliver. Luckily he's tough and will simply pass them in a few days... which is gross.

Meanwhile, back inside Palmer Technologies, Larvan made another threat to Felicity by taking over all the video monitors in the building. This reveals that the villain is inside the CEO’s office and not with her hostages in the boardroom. Felicity hatches a plan to sneak her mother and the hostages out through the decommissioned Arrow lair inside the building. She manages to get the others to safety, but she and Thea have to confront Larvan on their own in order to cover their escape.

She takes them back inside the office and reveals that she has a tumor wrapped around her spine. The only way to get it removed is a surgery that will leave her paralyzed — hence the reason she wants Felicity’s implant. Moved both by her story and the gun in her face, the CEO gives the villain blueprints for the device. However, when she looks at them and discovers how to make an implant of her own, the bee queen recognizes the code as that of the person who foiled her plans last year and sent her to jail. She returns to Felicity’s office with a strange wind blowing in her hair and her swarm of bees looking more volatile than ever.

Meanwhile, back at the bunker, Curtis is thrilled that they were able to bounce back from Plan A, but a disgruntled Oliver gives him a harsh lecture about taking this work seriously that almost makes him cry. Laurel pulls the hero aside and asks what’s going on and he reveals that, without Felicity, he doesn’t understand why he’s supposed to continue being the beacon of hope the city needs. In a relatively tender moment between the two characters, Laurel explains that he’s capable of saving the city, so he needs to keep going. He and Curtis make up in a very macho manner and the team returns to the Palmer Tech building for another shot.

This time, Diggle and Laurel hold off the Bee Man while Oliver rushes in and saves Felicity from Larvan. The Bee Man comes back and nearly beats the Green Arrow, but Curtis’ hacking skills manage to save the day and the team comes out safe and victorious once again. However, that doesn’t mean it’s all smooth sailing for the “Arrow” gang. The episode ended on a strange cliffhanger as Malcolm Merlyn (John Barrowman), who previously visited Damien Darhk (Neal McDonough) in jail to tell him that H.I.V.E. is moving forward without him, reveals that he’s now working with none other than Andy Diggle (Eugene Byrd).

“Arrow” airs Wednesdays at 9 p.m. EDT on the CW.