During the closing moments of "Arrow" season 4 premiere, the scene shows a grave being visited by The Flash and Oliver Queen. Now, the identity of the person underneath the grave will be revealed in episode 18, according to spoilers.

Showrunner Marc Guggenheim said as much in an interview with TVLine as he said, "I think promos have made it clear this is the episode you find out who's in the grave."

"We started off this year with the promise of a death," he added. "And when we worked our way through our various creative choices, we realized that the thing that will give us the most pop going into the end of the season, into next season, unfortunately would be..."

But he said that they have not always been afraid of killing of a major character if the story called for it, especially now when they are entering season 5.

He also said that there's going to be some revelations that will rock the relationship between Diggle and Andy.

The synopsis for episode 18 for "Arrow" season 4 offers plenty of spoilers as it reads:

Oliver (Stephen Amell) and Diggle (David Ramsey) learn that Merlyn (John Barrowman) is going to try to break Darhk (guest star Neal McDonough) out of prison. Meanwhile, Laurel (Katie Cassidy) gets a surprising offer and Felicity (Emily Bett Rickards) has a heart-to-heart talk with Curtis (guest star Echo Kellum). Rob Hardy directed the episode written by Marc Guggenheim & Keto Shimizu (#418).

Watch out for more spoilers for "Arrow" season 4 which will be published here when they come along.