"The Vampire Diaries" season 5 is coming this fall, and audiences can expect to learn about the mystery of the doppelganger. At the CBS Summer TCA All-Star event, Wetpaint Entertainment spoke with executive producers Julie Plec and Caroline Dries for answers about the strange phenomenon.

Spoiler alert! The season 4 finale brought a huge shock to viewers: Stefan Salvatore (Paul Wesley) has a doppelganger, and its "The Vampire Diaries" evilest and most unpredictable villain, Silas. This adds to Elena Gilbert's (Nina Dobrev) doppelganger, Katherine.

"Now that we realize Stefan's a doppelgänger, we kind of explore the deeper mythology of why does this weird phenomena occur. So that's pretty cool. And that has ripple effects for all of our main three characters," Dries told Wetpaint.

"It's our next layer of supernatural mystery that we haven't truly explored yet," Plec added. "So it's a season of the doppelgänger."

But not everyone has a doppelganger, according to the producers of the CW series.

"The mystery of how the doppelgänger was created and why and how often they appear and for what reason is something that we actually start getting into right away. And by Episode 3, we start laying a lot of the answers to that mystery out," Plec said.

Dries also warned the audience that the first episode will feature a "heartbreaking story" for many of the characters. Plec said Stefan is "just screwed" while he drowns over and over again at the bottom of the quarry, waiting for his loved ones to realize that he's missing.

But Plec said Stefan's storyline adds to intensity of the season.

"The Stefan storyline in episode one is really moving, and keeps alive that sense of his strong feelings for both his brother and for Elena," she said.