Daily told TV Line that the upcoming season, which will be the show's last, will refer back to the start of Desperate Housewives.
He said: "There is a big reveal at the end of the first episode that ties us back into the first season in an interesting way."
Daily also teased that the mystery will have something to do with Mary-Alice Young (Brenda Strong), who killed herself in the first ever episode and has since provided the show's narration.
Strong has recently revealed that she is looking forward to having a "bigger presence" in the new season, but Daily clarified that Mary-Alice will not turn up alive.
"She's dead," he said. "We're not going to mess with the DNA of the show. We're going to pay homage to it."
Miguel Ferrer, Andrea Parker and Charles Mesure have all signed up to appear in the final season of Desperate Housewives, which will premiere on September 25 on ABC.
Watch a look back at Desperate Housewives below: