"Sherlock" creator Steven Moffat unveiled last week the first photo from the upcoming season, giving some clues about where the series is headed.

The photo shows Benedict Cumberbatch and a canine companion, hinting that season 4 could be taking on "The Hound of the Baskervilles" this time. The bloodhound in the still is reportedly just a temporary companion of Sherlock and is not meant to take the place of Doctor Watson. It is presumed to be the sniffer dog named "Toby" which Sherlock uses in "The Sign of Four."

According to Moffat, the next season could be "Sherlock's" last, as Benedict Cumberbatch and Martin Freeman's plates are both full. This year, Cumberbatch is set to make his debut in the Marvel Cinematic Universe as the titular protagonist of "Doctor Strange." On the other hand, Freeman recently joined the MCU in "Captain America: Civil War," after leading the "Hobbit" trilogy as Bilbo Baggins. He also played a major role in the first season of "Fargo."

"I don't know how long we can keep it going," Moffat told Telegraph in an interview.

"I'm personally willing, but I'm hardly the main draw. I would be moderately surprised if this was the last time we ever made this show. But it absolutely could be," he added.

The last time fans saw Sherlock and Watson was in January, in "The Abominable Bride."

Season 4 is set to feature Toby Jones as a classic villain. Asked for more details about his role next season, the actor told Radio Times, "The only thing I'm allowed to reveal is that I'm indeed a baddie. I think that even, I'd say, I'm really bad."

"Sherlock" season 4 is expected to air in early 2017.