The Showtime drama's latest run will pick up where season six left off, with Deb (Jennifer Carpenter) having discovered Dexter (Michael C Hall) committing a murder.
"Viewers might think we shy away from that moment of Debra walking in and seeing Dexter stabbing into Travis's chest, but it's just the opposite," Buck told TV Guide.
"She now has to deal with what she's seen and what she knows. And it forces him to defend and define himself."
Buck also confirmed that the series will continue to explore Deb's romantic feelings for Dexter, a storyline that proved controversial with some fans.
"It's ironic that people are fine with Dexter jabbing people in the heart but mortified by this romance," Buck said. "We're not shying away from those feelings of hers."
Jennifer Carpenter recently told Digital Spy that she only plans to film eight seasons of Dexter.
"I think I'm gonna do eight," she said. "I just don't think that we want to overstay our welcome,"
The new season of Dexter will premiere on Sunday, September 30 on Showtime. In the UK, the series airs on FX.
> Dexter casts Avatar actor Matt Gerald for season seven
> Dexter casts Katia Winter in seventh season
Watch a teaser trailer for Dexter season seven below: