The upcoming season four episode 15 in "Arrow" TV show is called "Taken." The episode will feature the live-action debut of Vixen.
According to Blastr, in the upcoming episode Oliver Queen realize that he needs help battling Darhk. In order to do this, he will call for help on his friend Mari McCabe, aka Vixen.
Once arrived in Star City, Vixen will join Team Arrow. She will help fight against Damien Darhk in order to save William, Oliver's young son, who's been kidnapped by the villain. Vixen is able to get a lock on Darhk's location by using her magical ability to summon animal powers. Then all Team Arrow will go to war. Thea will have a heart-to-heart talk with Malcom.
Meanwhile, Oliver will have to reveal his identity once again, in order to save his son, according to TV Overmind. Since the first season, the number of people who know Oliver's identity as the Green Arrow has significantly grown. Many of those who found out Oliver's secret identity have secret identities of their own.
Since the beginning of this season the growing fear is that Damian Darhk, this year's villain, would be the next to discover Oliver's real identity. However, recently released photos from "Arrow" Episode 15 prove that it is someone else entirely who learns Oliver's identity. His baby's mother Samantha is allowed into the inner sanctum and learns who the Green Arrow is.
This week the entire team will find out about Oliver's son William being kidnapped by Damian Darhk. They will organize quickly to help getting the little boy back to his father. Oliver has to inform Samantha about his secret identity in order to make her trust he can help.
Samantha not only learns about Team Arrow and Oliver but she will be also actively involved in helping to get her son back. In order to do this, she will work alongside with Team Arrow.
