The Sign of Four (Penguin Classics)

As a dense yellow fog swirls through the streets of London, a deep melancholy has descended on Sherlock Holmes, who sits in a cocaine-induced haze at 221B Baker Street. His mood is only lifted by a visit from a beautiful but distressed young woman - Mary Morstan, whose father vanished ten years before. Four years later she began to receive an exquisite gift every year: a large, lustrous pearl. Now she has had an intriguing invitation to meet her unknown benefactor and urges Holmes and Watson to accompany her. And in the ensuing investigation - which involves a wronged woman, a stolen hoard of Indian treasure, a wooden-legged ruffian, a helpful dog and a love affair - even the jaded Holmes is moved to exclaim, 'Isn't it gorgeous!'

For more than seventy years, Penguin has been the leading publisher of classic literature in the English-speaking world. With more than 1,700 titles, Penguin Classics represents a global bookshelf of the best works throughout history and across genres and disciplines. Readers trust the series to provide authoritative texts enhanced by introductions and notes by distinguished scholars and contemporary authors, as well as up-to-date translations by award-winning translators.

Arthur Conan Doyle (1859-1930) was born in Edinburgh and took a degree in medicine at Edinburgh University before becoming a doctor in Southsea. He began writing detective stories to supplement his income and 'A Study in Scarlet' (1887) introduced his finest creation, the hawk-eyed detective, Sherlock Holmes. 

Peter Ackroyd is a well known writer and historian. He has been the literary editor of The Spectator and chief book reviewer for the The Times, as well as writing several highly acclaimed books including a biography of Dickens and London: The Biography. He resides in London and his most recent highly acclaimed work is Thames: Sacred River.