Teased in last spring's season finale, the underground caverns that will one day become the Batcave are set to be explored when "Gotham" returns in late September. However, for those who just can't wait a few more weeks, the Fox drama has released a photo that shares a glimpse of what Alfred and Bruce have discovered underneath Wayne Manor.

Debuting via TV Insider, the photo shows Bruce (David Mazouz) and Alfred (Sean Pertwee) venturing into the secret underground chamber for the first time.

"It changes everything in Bruce's life," Mazouz tells TV Insider of the discovery. "It changes how he sees Alfred, the criminal side of Gotham, even how he sees his parents. It's definitely not the Batcave. What is down there are clues to Thomas Wayne's secret life and what he was trying to do before being killed."

Starring Ben McKenzie, Donal Logue, Mazouz, Pertwee and more, "Gotham" returns to Fox on Monday, Sept. 21 at 8 pm EST.