[Warning: Spoilers ahead for Tuesday's episode of The Flash, "The Sound and the Fury."]

The Pied Piper (Andy Mientus) came to Central City Tuesday, forcing Harrison Wells (Tom Cavanagh) to make a bold move, and setting the stage for a big reveal about The Reverse-Flash's endgame.

Pied Piper, who in the show and the comics has the ability to manipulate sound waves, was hell-bent on revenge for becoming hearing impaired after the particle accelerator accident.

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In a departure from the comics, Hartley Rathaway (Pied Piper) was made a former Wells protege, who warned him the particle accelerator experiment could end in disaster. In an attempt to stop Hartley Rathaway's (Pied Piper) rampage, Wells held a press conference, in which he admitted that he had been warned. It was a big move for Wells, who viewers now know is Reverse-Flash, the murderer of Barry's mother.

The Flash executive producer Andrew Kreisberg says seeing Wells make heroic choices is all the more painful, because viewers know he has bad intentions underlying each of his moves.

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"When you look back, you will see he has had a definitive reason for doing all of the things that he's done," Kreisberg told a handful of reporters Monday.

The Flash also mentioned The Speed Force, a key element from the comic books, for the first time, with Wells talking to his A.I. Gideon about his speed problems. In Flash lore, the Speed Force is a mysterious source power that certain individuals (Barry Allen included) tap in to for their speed. In the comics, Wells taps into the Speed Force using futuristic technology, as was hinted at in Wedneday's episode.

Kreisberg said it was a deliberate decision not to mention the Speed Force until this episode, because he and the writers must strive to satisfy fans of the comics without turning off unfamiliar viewers who might need a little warming up before getting introduced to concepts like the Speed Force.

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Kreisberg also discussed Pied Piper's intellectual complexity. While most The Flash villains have relied upon brawn, Pied Piper used his brains in an attempt to defeat Barry (Grant Gustin) and his STAR Labs colleagues. Hartley pulled a Joker ala The Dark Knight and allowed himself to be captured so that he could learn more about their operations.

"We wanted them to go up against somebody who is brilliant … somebody that they really had to outwit," Kreisberg said. "This one was really complicated, in that we had to do a lot of different things.

Kreisberg also spilled details of the next Flash/Arrow crossover, which will see Felicity Smoak (Emily Bett Rickards) and Ray Palmer (Brandon Routh) make the trek from Starling City when budding superhero Ray needs help getting his Atom project off the ground. Felicity, who flirted with starting a relationship with Barry when she visited Central City earlier in the season, has been courted by Ray, the new CEO of Queen Consolidated.

Felicity and Ray will appear in episode 18 of The Flash, which is called “All-Star Team-Up."

“It happens to come at a particularly bad moment for Barry, but that’s partially why we did it. The first episode with Felicity in episode four, she really came along in a time when her experience in being a part of a crime-fighting team definitely helped Barry overcome what he was facing that week,” said Kreisberg. "When she comes [back], he’s having a crisis of conscience that in some ways only someone like she can help him through.”

The Flash airs Tuesdays at 8 p.m. on The CW.

Email: Aaron.Couch@THR.com

Twitter: @AaronCouch