'Sherlock' season 4 air date, plot, trailer & update: teaser shows 'The Abominable Bride'; crossover with 'Dr. Who' will happen but over Mark Gatiss' dead body

BBC has released two retro posters that introduce "The Abominable Bride," a "Sherlock" special which will premiere on Jan. 1, 2016. Meanwhile, a crossover with another British hit "Dr. Who" will never happen, according to Mark Gatiss.

In the New Year special, BBC's "Sherlock" will take us back to 1895 London with Sherlock Holmes (Benedict Cumberbatch) and Dr. John Watson (Martin Freeman) to the mystery behind the "Abominable Bride."

According to Comic Book Resources, the "Bride" is Mr. Thomas Ricoletti's wife dressed in her old wedding gown.

"Why is Thomas Ricoletti a little surprised to see his wife dressed in her old wedding gown? Because, just a few hours before, she took her own life..." BBC wrote on their website.

"Mrs Ricoletti's ghost now appears to be prowling the streets with an unslakeable thirst for revenge. From fog-shrouded Limehouse to the bowels of a ruined church, Holmes, Watson and their friends must use all their cunning to combat an enemy seemingly from beyond the grave and the final, shocking truth about... the Abominable Bride!"

Her ghost reappears for revenge, but to whom? The answers to the mystery will reveal itself when the special airs on Jan. 1, 2016.

Watch the teaser below:

Mark Gatiss, the co-creator of "Sherlock" and Mycroft Holmes' actor confirms that there will be no crossover with the hit British show, "Dr. Who" anytime soon. If there will be, it will be over his "dead body."

"I'm not being horrible, but I just don't see the point," Gatiss told Entertainment Weekly. "First of all, they are entirely different shows. But I think there'd be so much excitement among certain members of the fan community followed by massive disappointment that it wasn't the version they had in their heads. And, just personally, I've never been [a] fan of these kinds of mash-ups."

Another showrunner, Steven Moffat who is also the lead writer for "Dr. Who" wanted to have a crossover, but his collaborators aren't enthusiastic about it.

"I work with boring people on both shows," Moffat said, joking during an interview at Comic-Con. "I'd do it, 'cause it'd be funny. It'd just be a laugh. But the rest of them, frankly, the grownups - 'No, you can have too much sugar.'"

"Sherlock: The Abominable Bride" also stars Rupert Graves, Una Stubbs, Amanda Abbington and Louise Brealey. It will premiere on PBS and BBC One. A theatrical version will have 20 more minutes of additional footage in theaters in the U.S. and U.K.