The honeymoon period is over for Penguin and the Riddler on Gotham.

Things went south for the villainous friends when they turned on each other in Gotham's third season. However, Nygma is free of Mr. Freeze's ice block in season four and that's putting Oswald Cobblepot on edge.

“We know that Ed escapes and that is an extremely terrifying moment for Oswald because, again, Oswald when he’s at his lowest its when he has no control," Robin Lord Talor tells ComicBook.com. "Nygma is the only person who could meet Oswald on his level in terms of intellect and cunning. Now that he cannot control him anymore it's terrifying and threatening to him.”

Even though they may be rivals now, there will always be a lingering respect from their time working together that influences how they treat each other.

“I think that there will always be respect between the characters," Cory Michael Smith says. "I think their relationship was so personal and intimate, I don’t know that there’s another character that understood Ed the way that Oswald did and I think vice versa. So I think there’s such a connection there and such a fear of the other and a respect of the other that that will constantly be there.”

However, the Riddler who returns in Gotham's fourth season isn't necessarily the same Riddler who worked with Penguin during season three. Fans will see how that influences their dynamic when Gotham returns on Sept. 21.

Before there was Batman, there was GOTHAM.

With a reputation synonymous with law and order, Commissioner James Gordon is one of the crime world’s greatest foes. Everyone knows the name. But what is known of Gordon’s rise from rookie detective to Police Commissioner? And what did it take to navigate the layers of corruption that secretly ruled Gotham City, the spawning ground of the world’s most iconic villains — the larger-than-life personas who would become Catwoman, The Penguin, The Riddler, Two-Face and The Joker?

Gotham is the origin story of the great DC Comics Super-Villains and vigilantes, revealing an entirely new chapter that has never been told. From executive producer/writer Bruno Heller (The Mentalist, Rome), this one-hour drama follows one cop’s rise through a dangerously corrupt city teetering on the edge of evil and chronicles the genesis of one of the most popular super heroes of our time.

Gotham was developed by Bruno Heller and stars Ben McKenzie as James Gordon, Donal Logue as Harvey Bullock, Sean Pertwee as Alfred Pennyworth, Robin Lord Taylor as Oswald Cobblepot/Penguin, Erin Richards as Barbara Kean, David Mazouz as Bruce Wayne, Camren Bicondova as Selina "Cat" Kyle, Cory Michael Smith as Edward Nygma/Riddler, Jada Pinkett Smith as Fish Mooney, Drew Powell as Butch Gilzean/Cyrus Gold, Morena Baccarin as Leslie "Lee" Tompkins, Nicholas D'Agosto as Harvey Dent, Jessica Lucas as Tabitha Galavan, and Michael Chiklis as Nathaniel Barnes/The Executioner.