WARNING: The following article contains spoilers for this week's episode ofGotham, "The Beginning...," which aired Thursday on Fox.

Throughout its five season run,Gotham has featured the debuts of many a Batman villain. From main characters such as Penguin, Riddler and Catwoman to recurring guests such as Joker, Mr. Freeze, Firefly and Adam Strange, almost all of the biggest members of Batman's rogues' gallery have appeared on the series in one form or another.

Plus, even though it would take the series' entire run before the Joker fully became the Clown Prince of Crime,Gotham found a way to incorporate a proto-version of Harley Quinn in Jeremiah Valeska's right-hand woman, Ecco.

Now, in the series finale, "The Beginning...," Ecco's brutal, surprising death opens the door for the arrival of the one, true Harley Quinn.

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Gotham hasa long history of teasing Harley Quinn. It first started with Barbara Kean, who at a time was believed to be the Fox series' answer to the Clown Princess of Crime. However, that theory was later pushed to the side. The producers of the series would keep teasing the character, but it would only be near the end ofGotham's fourth season that Ecco would be introduced.

At first, she only served as a necessary bodyguard for Jeremiah. But soon, she became a partner in crime. She started wearing a court jester costume, and other outfits that honored Harley's red-and-black color scheme. In "Ace Chemicals,"she even showed up on roller skates in a nod to Harley's New 52 comic book look. By all accounts, it seemed likeGotham had veered away from the usual Harley origin story and opted to transform Ecco into the Joker's partner.

However, the series finale brings that belief to a screeching halt. In "The Beginning...," Jeremiah wakes from his (fake) decades-long coma to terrorize Gotham City once more. With the help of Ecco, he enacts his plan. The two eventually find themselves in Barbara Kean's old Sirens club, where they intend to kidnap Jim's daughter, Barbara Lee. There, in the heat of the action, Jeremiah accidentally shoots Ecco.

Unfortunately, both villains recognize the wound as fatal. Jeremiah, however, isn't brokenhearted in the least. He shoots Ecco again, this time to finish her off, all while saying there are other fish in the sea.

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In the grand scheme ofGotham, this isn't the biggest character death, but it's still one that's surprising, considering Jeremiah's story arc. Now, with his body bleached and his mind fractured (even more than before), there is nothing left tying him to the Jeremiah personality. Unencumbered, he can fully become the Joker.

And the Joker, eventually, will find his Harley Quinn. With Ecco dead,Gotham is wiping the slate clean and letting fans know that this Joker will, eventually, find his Harley. What's more, it even gives a twisted origin story for the character's look. When Jeremiah comes across Dr. Harleen Quinzel in Arkham Asylum and manipulates her into falling for him, he will give her the same type of costume that was once worn by his first partner in crime.

An echo, if you will.

Gotham stars Ben McKenzie as James Gordon, Donal Logue as Harvey Bullock, David Mazouz as Bruce Wayne, Robin Lord Taylor as Penguin, Camren Bicondova as Selina Kyle, Erin Richards as Barbara Kean, Sean Pertwee as Alfred Pennyworth and Shane West as Bane. Season 5 and The Complete Series will be available on Blu-ray and DVD June 11.