THE sleuthing is far from elementary in Guy Ritchie’s sequel to his 2009 reinvention of Sir Arthur Conan Doyle’s fictional detective.

The dense narrative taxes what Hercule Poirot referred to as the “little grey cells”, connecting minuscule clues in Sherlock Holmes’s mind through high-speed flashbacks in a style familiar to fans of the TV series CSI: Crime Scene Investigation.

Sinewy plot strands will probably tie younger audiences in knots.

For all its intellectual rigour, this film often feels like ambitious action set-pieces which have been bolted together by the screenwriters.

Explosions and stunts are orchestrated at breakneck speed by Ritchie, whose repeated use of slow-motion bloats the film’s cumbersome running time.

Holmes (Robert Downey Jr) has cut a swathe through the criminal fraternity of late 19th Century London aided by trusty sidekick Dr John Watson (Jude Law), who is bidding farewell to crime-solving to marry Mary Morstan (Kelly Reilly).

Newspapers are filled with shocking headlines about anarchist bombings in Strasbourg and Vienna, the apparent overdose of a Chinese opium dealer and the death of an American steel magnate.

Holmes deduces these events are linked to Professor James Moriarty (Jared Harris) and the sleuth persuades Watson to join him on one final globe-trotting adventure.

En route, the double-act encounters gypsy fortune-teller Sim (Noomi Rapace) and Holmes’s brother Mycroft (Stephen Fry), who is well-connected in the British government.

A battle of wits with Moriarty becomes personal when the diabolical professor promises to make Watson and his new wife suffer.

“When two objects collide, there is always damage of a collateral nature,” threatens the scholar, who is protected by a sharp-shooting lackey, Colonel Sebastian Moran (Paul Anderson).

Downey Jr and Law ease back into familiar roles, Rapace is feisty in her first English-speaking role and Harris chews on every syllable with menacing intent.

Eddie Marsan and Geraldine James reprise their roles as Inspector Lestrade and landlady Mrs Hudson respectively.