Oliver (Stephen Amell) and Felicity (Emily Bett Rickards) may have rode off into the sunset together in Arrow's third season finale, but the couple's problems are far from over.

Oliver, who is finally happy at the start of Season 4, will find his new sunny worldview challenged when he and Felicity return to vigilantism to face off against their most evil opponent yet, Damien Darhk (Neal McDonough).

But balancing work and love won't be easy. "We really wanted to explore the ups and downs of a traditional TV relationship, like we've established with Oliver and Felicity, and pretty much throw everything at it that we can and see if they'll make it through," says executive producer Wendy Mericle.

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At least Felicity will have a new confidante when the show returns: fellow tech-genius Curtis Holt (Echo Kellum), the future Mister Terrific. "He's going to fill the void that Ray left, not as a romantic interest for Felicity, but as someone who is an equal intellectually to her and that we can have fun scenes between her and Curtis Holt in Palmer Tech," Mericle says.

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