It's clear from the wording of the synopsis for Sherlock special The Abominable Bride that there's more than meets the eye to the ghostly woman of the title. "Mrs Ricoletti’s ghost now appears to be prowling the streets with an unslakeable thirst for revenge.... Holmes, Watson and their friends must use all their cunning to combat an enemy seemingly from beyond the grave..." But that doesn't stop the new trailer for the episode being very spooky...

In one rather chilling moment, the ghostly bride glides towards Holmes and Watson, while in another she creeps up behind John. But then a phantom using a gun? That seems a bit unnecessary. So what is going on in Sherlock and John's 19th-century adventure? We'll have to wait until 2016 to find out...

Sherlock: The Abominable Bride is on BBC1 on New Year's Day at 9pm