Bart, who has previously starred in series such as Desperate Housewives and The Event, recently signed up to play a wealthy, pretentious journalist in Revenge.
Kelley has now revealed that Emily (Emily VanCamp) will attempt a "pretty elaborate takedown" on Bart's character, TV Line reports.
"We found a really strong way to introduce a villain we quite like," he said. "Emily ends up using what she knows of Amanda from juvie to help her in her quest to destroy [him]."
Kelley continued: "The takedown just so happens to open up a whole new vein of intrigue and surprise and possibility that will have a great impact on Emily's quest. It paints villains in a softer light and makes people you like seem a little darker."
James McCaffrey and William Devane are among the other stars who have signed up for guest roles in Revenge.
The show returns with a new episode tonight at 10/9c on ABC.