The third season finale will feature extensive flashbacks focusing on Elena's (Nina Dobrev) life prior to the series, before the death of her parents and her first meeting with Stefan (Paul Wesley).
In an interview with Zap2it, Plec confirmed that the episode will feature the car crash in which Elena's parents died, but added that there will be no shocking supernatural twist on the event.
"[The use of flashback] is going to lead a lot of people to think 'Oh, they're going to reveal something huge about the way that accident went down'," Plec predicted. "I will still say what I said three years ago. That was an accident, period, end of story, no supernatural influence."
She continued: "The flashback in the finale is a nice, small little runner that goes through the entire episode as Elena is looking back on a part of her life when things were just more simple, at least from a supernatural level."
Aunt Jenna (Sara Canning) will return during the flashback sequences, while Elena's parents will be played by Jason MacDonald and Erin Beute.
Plec went on to discuss the role of Matt (Zach Roerig), whom Elena was dating at the time of the flashbacks.
She teased: "Matt is one of the vestigial representatives of this life that was clean and simple for [Elena]. Their friendship dates back to when they were in the sandbox together.
"We get a nice little flash of what it was like when they were dating, and that they were themselves a troubled relationship. Even though she's remembering a simpler time, her problems were actually just as complicated."
Plec recently promised "romance and heartbreak" from the finale, and confirmed that Elena will choose between Stefan and his brother Damon (Ian Somerhalder).
The Vampire Diaries continues on Thursdays at 8/7c on The CW. In the UK, the series airs on ITV2.
Watch the promo for the next episode 'Before Sunrise' below: