The BBC One series Sherlock reworks the original tales of the great detective Sherlock Holmes and his assistant Dr Watson, starring Benedict Cumberbatch and Martin Freeman, respectively. This overview of the programme is chiefly an aid to memory; it has averaged about two episodes a year over its seven-year run. The latter portion of the programme is discussed in revealing detail towards the end, preceded by a paragraph warning of the spoilers.

Steven Moffat and Mark Gatiss began this tale in 2010 and have set it in the present day. It boasts numerous innovations, from the tilt shift photography in the titles (making Piccadilly Circus seem like an intricate special effects miniature) to the inclusion of modern information technology. The stories are also presented at high resolution, compared to past adaptations: we're given a more detailed look at both the objects in vision and the minds of the characters.

Sherlock's three-episode series format is about as brief as one can get whilst still delivering more story than a trip to the cinema. This maximises the production resources allocated each episode, giving the look of cinema a run for its money.

A hallmark of the programme is its use of motion graphics, which convey thoughts without the use of voice overs and relate the content of observed text without the need for cutaways to the text observed. Also notable is Watson's blog, a small nod to the books' convention of the doctor as narrator. Its online readership becomes an element of the stories.

Whilst making free with the original stories, the episodes themselves are a treat for devotees of the Sherlock Holmes books. Throughout the programme there are nods to both major storylines and obscure details.

Series One begins with the introduction of John Watson as a war veteran (Afghanistan) with a healing quest that's a mystery in itself. This balances the character well against the activity of Sherlock, whose period eccentricities are expanded into modern-day excesses that make him even more in need of a decent foil. The pair get to know each other throughout the series, culminating in a confrontation with Sherlock's most famous nemesis, Moriarty. He's a fresh, modern maniac with decades of well-written baddies acknowledged and integrated.

Sherlock's Brother Mycroft is quite prominent in the programme. In the books, it's said he surpasses Sherlock's talents but hangs back, as he "would rather be considered wrong than take the trouble to prove himself right." The detectives' landlady Mrs Hudson is also embellished, justifying the precious time allocated the character.

The Detective Lestrade character has years of good police television woven into his fibre. Completely new to the myth is pathologist Molly Hooper. The young Sherlock of this programme is a bit pretty and Molly's awareness of it explores an angle that would be a mistake to ignore.

Series Two initially feints from Moriarty and sets Sherlock against Irene Adler, his intellectual match and a dominatrix to boot, as it were. The middle adapts the famous Hound of the Baskervilles tale and the climax sets Sherlock and Moriarty so well against each other that their mutual destruction seems certain.

What sort of person could join the celebrated team of Holmes and Watson on equal footing? What skills would they have? The answers are in the character of Mary Morstan, John's girlfriend at the start of Series Three. A mystery of her true identity soon begins to unfold. The series finale sets all three against the unimaginable: Magnussen, a mastermind who could not be outwitted. No, really. As the trio's final confrontation with him nears, we get psychological insights into them that truly complement the work of Conan Doyle.

Series Three's inclusion of Wanda Ventham and Tim Carlton as the brothers' parents is a treat for viewers, as they're Cumberbatch's parents and Ventham appeared three times in Doctor Who, before Moffat became its current showrunner.

One episode exists between Series Three and Four, apparently set in the Victorian era. It's delightful and concerns a mystery from long ago with clues toward the fate of a major character in the present day.

Series Four begins with a classic puzzler, mixed with another chapter in Mary's story. It's the greatest test of John and Sherlock's friendship yet and its aftermath may leave the viewer wondering if the entire programme has come to its conclusion.

At this point going further will reveal things about the series you may not wish to read without having first seen the episodes for yourself. If you have done so or you simply don't mind having various and sundry plot details revealed to you then feel free to proceed to the rest of this piece. End of warning.

The programme appears to climax at the end of Series Three, three whole years before its most recent episode. To protect John and his new family from blackmail secrets locked into Magnussen's photographic memory, Sherlock shoots the mastermind at point blank range. It's an act of programme-ending proportions.

For his adopted family, Sherlock sacrifices both himself and the regard many viewers had for him. The bureaucratic erasure of the act by Sherlock's brother does nothing to mitigate its impact. The writers appear to have chosen the hero's moral death instead of his friends' physical death.

In death, Magnussen has perhaps defeated Sherlock. Episode One of Series Four shows the great detective in fear of a children's story about The Grim Reaper; it presents him as a man on the run from inevitable fate.

Sadly, we lose Mary despite Sherlock's self-sacrifice. The sequence of events in her doom is somewhat replayed at the end of Series Four when a prison warden tries to make a bargain similar to Sherlock's.

Another reading of the dark finale is that Sherlock is such a high-functioning force of nature that Magnussen's murder is not a character-damning event for him. Series Four perhaps expresses this through the revelation of Sherlock's criminally-insane sister Eurus. She exists on a psychological plane symbolically illustrated as a passenger jet aeroplane: elevated, out of control and strewn with bodies. Like Sherlock, Eurus is malformed: a child in a complex vehicle. Her pleas for help are brutally violent but even more shocking is that they are ultimately successful.

Faced with an opponent he can neither outwit nor destroy, Sherlock is pulled forcibly from his emotional shell and subsequently provides the support Eurus needs from him. He finally understands the meaning emotional context gives to life and death situations, even if Eurus remains beyond redemption.

Mary has an imaginary presence to John in Series Four following her death. She also appears on a pre-recorded DVD with posthumous condemnation for Sherlock. She appears to have anticipated the effect of her own harsh words and a second disc arrives at the very end of the series with warm accolades for both the detective and his sidekick.

That positive note has perhaps ended Sherlock. We're shown time healing Holmes and Watson in a joyous, concluding montage. If further episodes are made, Moffat and Gatiss have quite a developed detective to work with. Will Sherlock and Molly become closer? Are texts from Irene in Series Four the beginnings of something more? Has Watson, the old soldier, new things to teach a Holmes who has seen so much combat in the field?

Sherlock, by Steven Moffat and Mark Gatiss. Sherlock Holmes: Benedict Cumberbatch. Dr Watson: Martin Freeman. Mycroft Holmes: Mark Gatiss. Moriarty: Andrew Scott. Mary Morstan: Amanda Abbington. Detective Lestrade: Rupert Graves. Mrs Hudson: Una Stubbs. Molly Hooper: Louise Brealey. Eurus Holmes: Sian Brooke.