‘Matilda Briggs was not the name of a young woman, Watson,’ said Holmes in a reminiscent voice. ‘It was a ship which is associated with the giant rat of Sumatra, a story for which the world is not yet prepared.’

(‘The Adventure of the Sussex Vampire’, from Sir Arthur Conan Doyle’s The Case-Book of Sherlock Holmes, 1927)

This is the flourish by which Doyle introduces both the most infamously proportioned Indonesian rodent in fiction and the greatest detective case that never was. It is a consummate tease of a throwaway line; the flippancy of Holmes’ reference, and the lack of any elaboration upon it, would have had Dr. Watson-the-chronicler spluttering. Is Holmes alluding to an actual animal? If so, what kind, and why would Holmes be involved? Thrown against the familiar surrounds of their Baker Street apartment it does not matter whether the rat in question is a plumpish pet or a whiskered Colossus as ferocious as the Baskerville Hound: the reader’s interest is immediately piqued. The many theories that have sprung up to explain the rodential reference, alongside the number of (parodic and otherwise) Sumatran rats that scurry through literature and cultural media, attest to its appeal as an ingenious, inexhaustibly engaging trope.

Part of the appeal of the Sumatran mystery must lie in the fact that it concerns, specifically, a rat. This is an animal that tends to fall automatically into the villain bracket; although oft-maligned, fictional mice and shrews are not presented as malignant forces to nearly the same extent. This prejudice is discernible in cliché and fable alike - if ‘mouse’ took the place of ‘rat’ in dirty rat, drowned rat, I smell a rat, love-rat, the rat-race and so forth it would lose much of its invective clout. Indeed, such phrases would become positively endearing. Umberto Eco, in Mouse or Rat: Translation as Negotiation, stresses the importance of translating Hamlet’s words as he slays Polonious behind the arras (‘How now? A rat? Dead, for a ducat, dead!” [III, iv, line 23]) so that the line reflects both the implied horror and righteousness on the part of the killer and a sense of sneakiness concerning the hidden pest.

Rats have been cast in henchmen roles since ancient times; Apollo sent a swarm (the correct, glorious collective noun is ‘a mischief’) of rats against Crinis for abusing his role as priest. Rather disappointingly, Crinis repented before the rats could have their nibbly way with him, and Apollo exterminated the lot with his arrows. That rats can arise in vast numbers and spread plague - a topic played with by Fred Saberhagen’s pastiche The Holmes-Dracula File (1992) - may explain some of the cultural horror associated with the creatures, but even as individuals they have often implied menace. In Egyptian lore the rat symbolises ‘utter destruction’; in the Japanese folktale ‘The Boy Who Drew Cats’ a city is beset by a mammalian proto-Godzilla in the form of a huge demonic rat; Scottish folklore hints at a sometimes-glimpsed, never-captured cryptozoological ‘Lavellan’, a massive rodent based in the waterways of Caithness. There are endless instances in contemporary fiction where rats are used instrumentally to represent anything on the scale between wily skulduggery and sheer evil. One of Patrick Bateman’s most unpleasant cruelties is meted out with a rat’s assistance in Easton Ellis’ American Psycho and, for the Everyman character of Winston Smith in Orwell’s Nineteen Eighty-Four, rats figure as that which ‘you can’t stand up to, can’t even think about’.

Beyond fiction, horror of rats has been ripe territory for psychoanalysis. Freud’s case-study of Obsessional Neurosis tellingly involved a ‘Rat Man’, so-named after the subject of many of the patient’s fantasies. Bacteriologist Hans Zinsser offered an explanation for mankind’s repulsion towards rats in his 1935 work Rats, Lice and History, suggesting that

[T]he natural history of the rat is tragically similar to that of man … some of the more obvious qualities in which rats resemble men [include] ferocity, omnivorousness… adaptability to all climates [and] the irresponsible fecundity with which both species breed at all seasons of the year with a heedlessness of consequences, which subjects them to wholesale disaster on the occasional failure of the food supply.

Here, fear of rats stems from an uncanny resemblance to humankind - ‘uncanny’ in the Freudian sense, whereby the reader undergoes a cognitive dissonance with the subject and finds themself attracted to, yet repulsed by, a familiar-but-foreign object.

Even those few instances of ‘good’ rats in fiction are somewhat tentative. For example, the much-loved ‘Ratty’ in Kenneth Grahame’s The Wind in the Willows was in fact a water-vole. In The Tale of Samuel Whiskers by Beatrix Potter (dedicated to the author’s pet rat Sammy, ‘the intelligent pink-eyed representative of a persecuted - but irrepressible - race and affectionate little friend, and most accomplished thief’), the eponymous Samuel is far from a hero in the classical mould. During the course of the book he and his wife try to bake Tom Kitten into a roly-poly pudding, and they are only stopped from doing so when their over-exuberant use of the rolling-pin alerts the victim’s mother.

The reader is primed, then, to expect villainy from Holmes’ mysterious rodent. That it is giant, however, offers a whole new layer of intrigue: something already horrid is inflated into a grotesque, its flaws exposed onto a Gargantuan scale. Correspondingly, over-sized rats gambol rampant across books and screens alike. Often they are deployed camply and outlandishly for laughs, such as the ROUSes (Rodents of Unusual Size) in the book and film of The Princess Bride, or in the New Avengers and Red Dwarf.

More sinister giant rats horrify in H.G.Wells’ The Food of the Gods and How It Came to Earth and in Stephen King’s short story ‘Night Shift’.

A particularly large rat crops up to terrorise a young hero in Bram Stoker’s ‘The Judge’s House’. Stoker’s hero Malcolmson has a certain bluffness and ardent belief in logic that any fan of Holmes and Watson would recognise: ‘But, my dear Mrs. Witham,’ says he at the beginning of Stoker’s story, ‘indeed you need not be concerned about me! A man who is reading for the Mathematical Tripos has too much to think of to be disturbed by any of these mysterious “somethings”, and his work is of too exact and prosaic a kind to allow of his having any corner in his mind for mysteries of any kind’. So blithe and so errant, Malcolmson; a warning to confident rationalists everywhere. When he first comes to blows with the rat, Malcolmson takes a swing at it with the nearest thing to hand that acts as a very symbol of his rationality: a book of logarithms. The book ‘was badly aimed and the rat did not stir’; the huge rat is thus figured not only as Malcolmson’s antagonist but explicitly set up as a brooding anti-logical nemesis, confounding a man of science and reason. It is an almost identical tension between rational man and ludicrous animal that forms part of the Sumatran rat’s appeal in the Holmes story.

There is an issue as to how ‘giant’ Sherlock Holmes’ rat could be, of course. In Stoker’s story it is eventually assumed there is a supernatural reason for its size, whilst science fiction sees a number of the animals swollen by radioactive or genetic meddlement. One way in which Holmes’ Sumatran rat may have been ‘greater’ than usual could be that it was actually many rats, a compaction of rodents into a so-called rat-king. This is a phenomenon that is believed to occur when a number of rats’ tails become enmeshed so that they appear to move as one single organism. A rat-king of ten rats was recorded in Bogor on Java in the earlier twentieth century: is Java close enough to Sumatra for this to be a guess at the ‘giant’ nature of Holmes’ animal?

Closer to Baker Street, it is not inconceivable that a large rat might be bred for fighting. Parliament brought in the Cruelty to Animals Act in 1835 that prohibited bull and bear fighting, but rat-baiting did not fall under its remit and was a popular sport for gambling. Might a giant fighting rat infringe these strictures and thus be of interest to Holmes in a criminal capacity? A super-size European rat may even have been fed up culinary purposes. In the Larousse Gastronomique there is a section on the rat as a possible delicacy: ‘during the siege of Paris in 1870, the old coopers (barrel-makers) would grill them [the rats] over broken barrel staves, after cleaning and skinning them. They would season with oil and plenty of shallot’. Presumably, the bigger the better.

There is a further possibility that Holmes’ rat was giant by dint of its very species. Perhaps it had been encountered by Holmes (or by his alter ego, the Norwegian explorer Sigerson) on his travels but could not be unveiled to the scientific community at that time. Rodents have inhabited the earth for an estimated 40 million years and are its most diverse group of mammals, with more than 2,000 species. Just last year a new giant rat was discovered deep in the jungle of Papua New Guinea that measured 82cms long, making it amongst the largest species of rat known anywhere in the world. It has been provisionally named the ‘Bosavi Woolly Rat’. Even more outlandish and outsized was the media-dubbed ‘giant guinea pig of Venezuela’, a prehistoric animal about the size of a buffalo whose remains were discovered in 2000. A rodent of such large dimensions is more likely to be found in Doyle’s novel The Lost World, but Holmes does specify that the world is not prepared for it…

The Sumatran detail is important, its Oriental otherness making the reference all the more intriguing and transporting the reader from the dour stereotype of Sherlock Holmes who clamps a mist-damp deerstalker on his head and slopes off to play the violin on a Devonian moor. The rat is not alone among shadowy Sherlockian fauna: besides the diabolical Baskerville Hound there are also throwaway references to a trained cormorant from a ‘case of the politician and the lighthouse’ (‘The Adventure of the Veiled Lodger’, 1927) and a ‘repulsive story of the red leech’ (‘The Adventure of the Golden Pince-Nez’, 1904). However, for sheer ludicrous exoticism none come close, and the rat’s mystique has spawned countless tributes and parodies.

From logically reasonable novels to a brilliantly cobbled-together Dr. Who episode, numerous works have leapt leapt upon the specifically Sherlockian rat. Pastiches that take on the subject are often ingenious in their explanations for the rat but in doing so sometimes squander the characters of Holmes and Watson. Two excellent pastiches, however, are The Giant Rat of Sumatra by Richard Boyer - where the ‘rat’ is in fact a tapir - and David Stuart Davis’ Shadow of the Rat. The rat looms large on stage too: at the end of Paul Giovanni’s play The Crucifer of Blood (loosely based upon Doyle’s The Sign of Four), sailor Mordecai Smith slumps forward to proclaim that he has seen the giant rat of Sumatra, only to fall into a faint from nervous shock. Philip Pullman’s play Sherlock Holmes and the Limehouse Horror affectionately spoofs the giant rat, whilst in Disney’s The Great Mouse Detective (1986) a certain Professor Padraic Ratigan emerges as the archenemy of the mouse Basil of Baker Street, voiced and sung by a fantastic Vincent Price (who later remarked that it was one of his favourite roles). In the book series by Eve Titus Ratigan is a mouse, but in the Disney adaptation Ratigan is clearly, and despite his own claims to the contrary, of the rat camp.

One of the best pasticheurs of Holmes in recent times has been Bert Coules; in his ‘Further Adventures’ he aims to flesh-out many of the referenced but unresolved cases of the Canon for dramatisation on BBC Radio Four. In an upcoming series Coules will tackle the enigma of the aforementioned ‘trained cormorant’ but shies away from tackling the giant rat because ‘the name is so iconic and Doyle’s line about the world not being prepared for the tale is so inspired, that expectations would be enormous’. Coules does, however, offer a fascinating springboard for Rat devotees: in conversation with actor and writer Mark Gatiss, they batted back and forth the idea that the Matilda Briggs story might hinge upon the fact that, in the Sumatran language, a ‘rat’ (pronounced ‘rart’) actually means ‘princess’. Holmes’ run-ins with British and Bohemian aristocracy resulted in some of the best of Doyle’s adventures: the Gatiss-Coules conception of a Sumatran ‘rat’ would be a most fascinating story indeed.

‘It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts.’

Arthur Conan Doyle permits Holmes these words in his story ‘A Scandal in Bohemia’ and it is with such a premise that Sherlockian scholar Alan Saunders offers one of the most winning explanations in conjunction with the giant rat. It calls upon beguiling evidence and includes a well-observed correlation between the name of the ‘Matilda Briggs’ ship and the daughter of the captain of the most famous mystery ship of all, the ‘Marie Celeste’. The connection Saunders makes concerns another of Holmes’ cases, ‘The Adventure of the Dying Detective’ and the former Sumatran resident that the reader encounters there. I will not reveal in full Saunders’ theory as to the rat’s identity; suffice it to say, the mind boggles, wonderfully.

The cormorant, the leech, the Sumatran rat: here, speculation is everything. This is storytelling by not telling whereby the reader is forced to struggle with a kind of narrative diaporesis, kept enthralled via a sleight of allusion in keeping with an almost Keatsian concept of negative capability. In a letter of 1817, Keats defined this as ‘when a man is capable of being in uncertainties, mysteries, doubts, without any irritable reaching after fact and reason’. No explicit revelation of the rat’s identity made by Doyle could ever be more powerful than its potential identity afforded by a reader’s undirected imagination. That is the charm of the giant rat of Sumatra: it has the intrigue of a cryptic crossword clue, the fantasy drama of science fiction and the baseline thrill of an old fashioned mystery.

Holmes often reproaches his long-suffering Watson along these lines: ‘You see, but you do not observe’. The giant rat is so alluring precisely because it will always evade attempts at direct capture. Much excitement lies in the literary chase and one cannot help but feel that the creator of Sherlock Holmes would approve of the questing spirit it has inspired and the number of pastiches, parodies and speculative essays that seek to infer, deduce and posit upon the nature of his rat. Ultimately, however, it is its sheer unknowability and the fact we can only ever consider it askance that endows it with such interest. Allusive and elusive, Holmes’ nonchalant reference leaves the reader flummoxed, provoked and subjected to a tension that will never be fully resolved. That is the rat’s mischievous appeal.

Sherlock by Nick Brown