The game's afoot and Sherlock and Watson have summoned us to an 'Urgent and Extraordinary' press conference" at 221B Baker Street to share details of their latest case.
With two hardened hacks grilling the great sleuth about his adventures with the fearsome hound of the Baskervilles, it's a neat entry into a story of inheritance, false identity, and the supernatural.
But this is immersive event theatre, so first we've had to find our way to the obligatory anonymous looking venue (in West Kensington) and step into the fictional world of the great consulting detective circa 1899.
We follow down a dark passageway papered with news cuttings, through the door of 221B, and into a velvet curtain-swagged room, lined with Victorian display cabinets touting everything from specimen jars to pistols and poisons.
Seated at our table, we're handed a bound menu of cocktails and drinks, and a folder of clues.
My mystery-loving teenager loved scouring the collection of cuttings, telegrams, maps and the last will and testament of Sir Charles Baskerville to prime ourselves on the suspects.
Over a Champagne cocktail and delicious starters of arancini and smoked duck with vodka grapes, we discussed theories about possible dodgy doctors, creepy servants, violent criminals, and fraudulent schoolmasters.
The Great Murder Mystery, by 'live experience' specialists The Lost Estate, has been done so cleverly that you really can deduce the identity of the escaped prisoner roaming Dartmoor - although the eventual murderer took us by surprise.
The drama is a well-edited largely faithful gallop through Conan Doyle's famous mystery, brought to life by five multi-tasking actors, atmospheric lighting, and a string trio whose music adds urgency and melancholy to the storytelling.
Here, it's the feisty Lady Henrietta Baskerville (Risha Silvera) who arrives from Canada to claim her inheritance, only to be beset with warning letters, a break-in and tales of a grisly family legend involving a demon hound who terrifies her ancestors to death.
Between each of the three performance sections, to cries of 'Mrs Hudson,' the fictional Baker Street housekeeper rustles us up two more courses, served by attentive waiters clad in period garb.
First a crowd-pleasing pimped up roast dinner with tender chicken wrapped around a truffle pate, crispy Pommes Anna, and peas in a pastry basket, then a lovely light cheesecake topped with fresh strawberries and a ball of Champagne sorbet.
As part of the experience you should try the inventive menu of themed cocktails.
Writer Kate Ferguson keeps the story moving briskly, avoiding waffly description, and director Simon Pittman delivers a taut murder mystery with a couple of twists at the end.
The hound itself is unseen, evoked only by a growl, and the frisson factor could have been dialled up by more potent effects.
But Samuel Collings is a suitably sharp and eccentric Holmes, and Stephan Boyce a decent and flummoxed Watson, and the whole package makes for a thrilling and special night out.
The Lost Estate's The Great Murder Mystery runs Thursday-Sunday with performances on 17th, 18th, 24th and 25th September and an additional evening show on Sunday 29th.
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