SPOILER ALERT: The CW’s Arrow had a major departure from the original cast on this evening’s show.

The superhero show, based on the DC Comics character Green Arrow, follows playboy Oliver Queen (Stephen Amell) who returns home after five years of being stranded on an island and decides to fight crime as a vigilante hero who uses trick arrows to foil his foes.

SPOILERS START HERE:

On tonight’s show, a major crossroads was reached, as one of the Team Arrow members decided that they had to leave town in order to right some major wrongs.

Thea Queen (Willa Holland), the maternal younger half-sister of Oliver Queen and a member of Team Arrow who goes by the name of Speedy, left the team and the town. Only four of the show’s series regulars from the beginning remain on the show.

Tonight’s episode saw Team Arrow dealing with a new threat, a rogue band of League of Assassins members known as the Thanatos Guild. The guild leader, Athena (Kyra Zagorsky), traveled to Star City in search of a map that led to some sort of ancient treasure, and the Thanatos Guild believed that Thea would be able to help unlock it.

Thea and love interest Roy Harper (Colton Haynes) reluctantly decided to help solve the problem with the Thanatos Guild, tracking down the map, and ultimately figuring out that it led to the existence of three new Lazarus Pits. That made Thea realize that she needed to go in search of the remaining pits, taking Roy in tow.

While fans had been expecting Thea’s departure because of her diminishing role in the series, her abrupt leave-taking still stunned. But wait – this may not be the end.

Arrow executive producer Marc Guggenheim indicated the door is open for a Thea return.

“We talked about some requests (Holland) had for us in terms of how her episodes would be utilized and grouped, and at what point in the season she would be written out, and we accommodated her on all those fronts because, look, at the end of the day, we love Willa and we love working with her,” Guggenheim told TV Line. “She’s done right by us and so we wanted to do right by her.”

Guggenheim said Holland wanted to reduce her episodic commitment, and so the producers worked with her to establish the where/when/how of it.