BBC 'Sherlock' Season 4 Air Date, Spoiler & Episode Premiere: Show's Creator Says Sherlock, John Watson Will Be in 'Deeper and Darker Water'

British film actor and "Sherlock" star Benedict Cumberbatch is rumored to be nearing engagement to his girlfriend of four months, former "Burlesque Fairytales" co-star Sophie Hunter.

The star of BBC "Sherlock" reportedly visited Hunter's hometown of Edinburgh, Scotland, where it's speculated that he asked his girlfriend's mother, Anna, for daughter's hand in marriage. It's also said that the couple took a tour of the Royal Botanic Garden during their vacation.

The low-key romance was only made public recently. Photographers first snapped photos of the pair sitting side-by-side at the French Open in Paris on June 10. Then, they made a public appearance at pianist James Rhodes' wedding on Sept. 27. Yet, the two kept their distance at the European premiere of "The Imitation Game" in London on Oct. 8. Also, later that evening, the two left the Corinthia Hotel, using separate exits.

If Cumberbatch were to marry, it would be his first marriage. His most recent long-term relationship was his 10-year bond with screenwriter Olivia Poulet, which ended in 2010. While he hasn't married yet, Cumberbatch has shared that he's looking to settle down.

"I would love to have children," he said. "Everyone wants to know when I'm going to settle down and who is going to be Mrs. Cumberbatch. I can't wait to do an interview like this and just talk about my child."

In unrelated yet always related "Sherlock" news, Season 4 of "Sherlock" is set to air during January 2016 following the Christmas episode special that will air during late winter 2015. The Christmas episode will show Sherlock in ways that's yet to be seen. And rumor has it that the episode will be based on the Sherlock Holmes story "The Adventure of the Blue Carbuncle."

Earlier this year, Sherlock Co-creator Mark Gatiss stated, "Series Four! At last! ... It's always special to return to Sherlock, but this time it's even more special as we're doing...a Special! Not only THAT, we'll then be shooting three more episodes, which will take Sherlock and John Watson into deeper and darker water than ever before...The whole 'Sherlock' team are terrifically excited to return for four new adventures. The Game is on -- again!"

Co-Creator Steven Moffat said, "A special, plus a new series of three episodes -- it's a record-breaking run! Of course, it's far too early to say what's coming, but we're reasonably confident that the very next thing to happen to Sherlock and John, is the very last thing you'd expect."