Here's the description off their website:
An experience inspired by the Sherlock Holmes novels, available to play 7 days a week until 1 September 2016. Limited availability - booking required.
Professor James Moriarty invites you to take part in a new cryptic challenge in partnership with HiddenCity and Time Out London. Your challenge: in teams of up to four people solve a trail of clues which he has personally prepared. Explore exhibitions celebrating contemporary architecture, drink in Georgian public houses, scrutinise 15th century art in a Mayfair townhouse and finally find his safehouse to receive an offer...
Strictly over 18s only. To gain entry to the safe house Professor Moriarty insists, 'no shorts or tracksuits be worn'
Start location: Ground floor of the Royal Institute of British Architects
Start Time: Start between 11:30am and 2pm (so 2pm is the latest start time).
Duration: 3-4 hours including two breaks.
Difficulty: Even Mr Holmes would be tested...
Local knowledge required: None.