<P> Sherlock is a television crime drama that presents a contemporary adaptation of Sir Arthur Conan Doyle's Sherlock Holmes detective stories . Created by Steven Moffat and Mark Gatiss, it stars Benedict Cumberbatch as Sherlock Holmes and Martin Freeman as Doctor John Watson . The first series of three episodes aired in 2010, while series two aired in 2012, and a third series aired in the first quarter of 2014 . The third series has become the UK's most watched drama series since 2001 . A single episode aired in 2016, as a Victorian - era special . Sherlock has been sold to over 200 territories . </P> <P> Sherlock depicts "consulting detective" Holmes, assisting the Metropolitan Police Service, primarily Detective Inspector Greg Lestrade (Rupert Graves), in solving various crimes . Holmes is assisted by his flatmate, Dr John Watson, who has returned from military service in Afghanistan . Although the series depicts a variety of crimes and perpetrators, Holmes' conflict with his archenemy Jim Moriarty (Andrew Scott) is a recurring feature . Molly Hooper (Louise Brealey), a pathologist at Bart's Hospital occasionally assists Holmes in his cases . Other recurring roles include Una Stubbs as Mrs Hudson, Holmes and Watson's landlady; and co-creator Mark Gatiss as Sherlock's brother, Mycroft Holmes . In January 2014, Moffat confirmed that the series would have a fourth series, and that a fifth series had been plotted . As of 15 January 2017, 13 episodes of Sherlock have aired, including one special, concluding the fourth series . </P> <Table> <Tr> <Th_colspan="2"> Series </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="2"> Average ratings (millions) </Th> </Tr> <Tr> <Th> First aired </Th> <Th> Last aired </Th> <Th> UK </Th> <Th> U.S. </Th> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> </Td> <Td_colspan="1"> 25 July 2010 (2010 - 07 - 25) </Td> <Td> 8 August 2010 (2010 - 08 - 08) </Td> <Td> 8.37 </Td> <Td> N / A </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> </Td> <Td_colspan="1"> 1 January 2012 (2012 - 01 - 01) </Td> <Td> 15 January 2012 (2012 - 01 - 15) </Td> <Td> 10.23 </Td> <Td> 4.4 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> </Td> <Td_colspan="1"> 1 January 2014 (2014 - 01 - 01) </Td> <Td> 12 January 2014 (2014 - 01 - 12) </Td> <Td> 11.82 </Td> <Td> 6.6 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="3"> Special </Td> <Td_colspan="2"> 1 January 2016 (2016 - 01 - 01) </Td> <Td> 11.64 </Td> <Td> 3.4 </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="1"> </Td> <Td_colspan="2"> </Td> <Td_colspan="1"> 1 January 2017 (2017 - 01 - 01) </Td> <Td> 15 January 2017 (2017 - 01 - 15) </Td> <Td> 10.00 </Td> <Td> N / A </Td> </Tr> </Table> <Tr> <Th_colspan="2"> Series </Th> <Th_colspan="2"> Episodes </Th> <Th_colspan="2"> Originally aired </Th> <Th_colspan="2"> Average ratings (millions) </Th> </Tr>

How many episodes are in sherlock season 1
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