What clues to the new Sherlock series can you see in the first sneak peek trailer… and is Tom Hiddleston set to join Benedict Cumberbatch?

SHERLOCK is back with a new mystery – and Tom Hiddleston is at its centre, ahead of the BBC show’s fourth series next year.

Writer Mark Gatiss set super-fans into a spin by posting a picture of himself with actor Tom and Sherlock star Amanda Abbington at the San Diego Comic Convention.

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Speculation is mounting that Tom may play Sherlock’s other brother Sherrinford in the new series.

Sherrinford is not a creation of original author Arthur Conan Doyle but appears in a biography of the fictional detective called Sherlock Holmes Of Baker Street: A Life Of The World’s First Consulting Detective.

Here, JEN PHARO dons her deerstalker hat to decipher the clues in a new 90-second trailer for the new series.

1 - Return of Moriarty

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SHERLOCK’S nemesis Moriarty blew his brains out in series two but Andrew Scott’s villain returns just the same.

“Did you miss me?” he taunts.

2 - Watson tragedy?

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DOCTOR WATSON (Martin Freeman) stands over a figure in a hospital’s intensive care unit.

But is that wife Mary who is in the bed?

3 - Action-packed series

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THE trailer lasts only 90 seconds but that is long enough for guns, fistfights and explosions.

This scene sees police marksmen descending from the ceiling, while Mary cowers under a statue.

4 - Mary's old tricks?

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MARY might be pregnant and happily married to John, but is her assassin past about to catch up with her again?

5 - Explosive scenes

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SHERLOCK must be struggling in the new series, as there is at least one explosion he can’t stop in time.

A fireball rips through a manor house in the new series.

6 - Sherlock's powers waning?

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HOLMES’ greatest weapon is his cunning mind, of course, but the ace detective could be forced to get his hands dirty . . .

7 - New villain

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TOBY JONES will play poisoner Culverton Smith, who is in Conan Doyle’s story The Adventure Of The Dying Detective.

8 - Lady of the manor

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LANDLADY Mrs Hudson (Una Stubbs) seems to have toughened up.

She lets Mycroft have it, telling him: “Get out of my house, you reptile!” What can he have done?

9 - Hallucinations?

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A SURREAL parade of nurses comes towards a clearly scared Sherlock (Benedict Cumberbatch).

Is it a hallucination? Has the detective succumbed to drugs again?

10 - Clue's in the name

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IN clues given by the cast, “Thatcher” refers to The Six Thatchers, an update of Conan Doyle’s The Six Napoleons.

-- Sherlock returns to BBC1 in 2017