Unseasonable heat and humidity on the evening of April 7, 1779, did not stop Londoners' usual pursuit of business and pleasure. Over in Whitehall, the first lord of the admiralty, the Earl of Sandwich, discussed with his harried colleagues the prosecution of the American war. A key strategist in bringing the 13 colonies to heel, Sandwich was a tall, rather clumsy man in his 60s known as a libertine, a passionate fan of the sport of cricket and a great patron of music, especially the work of George Frideric Handel. He was also a hardworking and ruthless politician. The snack that bears Sandwich's name, which was first made by slipping a slice of salted beef between two pieces of bread, was invented not, as legend would have it, to allow the earl longer hours at the gaming table but more time at the office. On this particular evening Sandwich's late-night labors—he had originally planned to go to the theater—were prompted by a pressing threat to his political career. The war in America was going badly, George III's administration was in disarray, and it looked as if Sandwich might be sacrificed to appease government critics.

Across town at the Covent Garden Theatre, where Sandwich had hoped to spend a more amusing evening, ladies and gentlemen, merchants and lawyers were pouring through the lobby for a benefit performance of the popular comic opera Love in a Village. These two events, seemingly unconnected and so different in character, were to be brought together by a terrible crime of passion perpetrated that night.

Among the evening's theatergoers was Martha Ray, Sandwich's 35-year-old mistress. Ray, the daughter of a corset maker, had been a milliner's apprentice before falling in with the earl. At this point, she had been Sandwich's mistress for more than 16 years, the mother of five of his six children, and his public consort. A contemporary described her as "not what we would call elegant, but which would pass under the denomination of pretty; her height was about five feet five inches; she was fresh-coloured, and had a perpetual smile on her countenance, which rendered her agreeable to every beholder." One admirer described her as "a second Cleopatra—a Woman of thousands, and capable of producing those effects on the Heart which the Poets talk so much of and which we are apt to think Chimerical."

While the earl labored over naval manifests and how to justify the war's growing expense (he survived the immediate crisis and remained first lord of the admiralty until 1782), Ray and her companion, the Italian singer Caterina Galli, took their seats close to the royal box, where they not only enjoyed one of the best views of the stage but were easily seen by the rest of the audience. The two women would be joined during the course of the evening by a number of male admirers with whom they would chat and flirt while the performance was in progress.

Across the theater in the pit, a tall, handsome young man in his 20s, dressed entirely in black, watched the earl's mistress. The Rev. James Hackman—according to the St. James's Chronicle, a "Person of Abilities,...descended from a very reputable family, distinguished for Taste and Delicacy of Sentiment"—was deeply infatuated with Ray and heartbroken at her rejection of his offers of love and marriage. Turning his back on this fashionable scene, he hastened to his lodgings close by the theater to retrieve two loaded pistols and to compose a note to his brother-in-law:

My Dear Frederick
When this reaches you I shall be no more, but do not let my unhappy fate distress you too much. I have strove against it as long as possible, but it now overpowers me. You know where my affections were placed; my having by some means or other lost hers, (an idea which I could not support) has driven me to madness.... May heaven protect my beloved woman, and forgive this act which alone could relieve me from a world of misery I have long endured. Oh! if it should be in your power to do her any act of friendship, remember your faithful friend.

Stuffing the note in one pocket together with one of the pistols, he put another letter—his rejected proposal of marriage—in his other pocket with the second weapon.

His pockets full of sentiment and violence, Hackman then returned to Covent Garden. He seems to have entered the theater several times during the evening (a full night's entertainment lasted nearly five hours), retreating to the nearby Bedford Coffeehouse to strengthen his resolve with glasses of brandy and water. His friends claimed that he then attempted to shoot himself on two occasions, first in the lobby, where he was prevented by the crowd from getting close enough to Ray to be sure that she would witness his death, and then on the steps of the theater, where he was pushed away from her by a man carrying the sedan chair of one of the theater's wealthy patrons.

At about a quarter past eleven, Ray and Caterina Galli came out of the theater, where the large crowd jostled them and prevented them from reaching their waiting carriage. John Macnamara, a handsome young Irish attorney, saw the two women, who, as a friend of Macnamara's put it, "seemed somewhat distressed by the crowd, whereupon he offered his service to conduct them to their carriage, which was accepted, and Miss Ray took hold of his arm." Threading their way through the swirl of parting spectators and down the steps of the theater, Galli entered the carriage first. Ray followed, putting her foot on the carriage step as Macnamara held her hand. At that moment, a figure in black dashed forward and pulled Ray by the sleeve; she turned to find herself face to face with Hackman. Before she could utter a word, he pulled the two pistols from his pockets, shot Ray with the one in his right hand, and shot himself with the other.

As the crowd shrank back, Macnamara, unsure of what had happened, lifted Ray from the ground and found himself drenched in blood. Years afterward he would recall (somewhat hyperbolically) "the sudden assault of the assassin, the instantaneous death of the victim, and the spattering of the poor girl's brains over his own face." According to author and gossip Horace Walpole, Hackman "came round behind [Ray], pulled her by the gown, and on her turning round, clapped the pistol to her forehead and shot her through the head. With another pistol he then attempted to shoot himself, but the ball grazing his brow, he tried to dash out his own brains with the pistol, and is more wounded by those blows than by the ball." Hackman writhed on the ground, "beating himself about the head...crying, Ôo! kill me!...for God's sake kill me!'"

With the help of a bystander, Macnamara, shocked but with great composure, carried Ray's lifeless body across the square and into the nearby Shakespeare Tavern, where she was laid on a table in a private room. Meanwhile, a passing constable had arrested Hackman and confiscated his pistols and the two letters in his pockets. Sir John Fielding, a magistrate (and the blind half brother of novelist Henry Fielding), was summoned, and he arrived at the Shakespeare at three o'clock in the morning. He committed Hackman to prison, to be held for questioning the next day.

A little more than a week later, Hackman went on trial for murder at a packed session of the Old Bailey courthouse. His lawyers entered a defense of temporary insanity. They argued that Hackman had yielded to a sudden and "irresistible impulse" prompted by a fit of jealousy at seeing Ray on the arm of another man. "I protest, with that regard for truth which becomes my situation," Hackman passionately testified, "that the will to destroy her who was ever dearer to me than life, was never mine, until a momentary phrenzy overcame me, and induced me to commit the deed I deplore." But the court, most likely persuaded by the existence of Hackman's second pistol, did not hesitate to find him guilty. Eighteenth-century justice was swift. Hackman was executed a few days after the trial before a vast crowd of onlookers. His last words, it was reported, referred to his "dear Miss Ray."

Hackman's crime prompted an orgy of speculation. There was never any doubt that Hackman had killed Ray—a large crowd of rich and fashionable theatergoers had witnessed the bloody deed—but why had he done it? Were Ray and Hackman actual lovers, or was Hackman an 18th-century John Hinckley stalking the Georgian equivalent of Jodie Foster, pressing his unwanted attentions on a public figure?

The newspapers quickly established that the couple had first met in 1775 at Hinchingbrooke, Lord Sandwich's country seat, but there was almost no public knowledge of what, if anything, had happened between that meeting and the murder four years later.

The tale of Ray, Hackman and Sandwich intrigued me both as a historian of the 18th century and a lover of detection. Surely it would be possible to crack the secret, to learn what lay at the heart of this love triangle and why Hackman had resorted to such terrible violence. As I probed, I came to conclude that the story's very inconclusiveness, its openness to interpretation, contributed to its fascination and helped explain why the case had been reopened, reexamined and reworked in many different forms—in prose and verse, history, biography, medical science and fiction. What began for me as the history of an event turned into a history of storytelling. The first newspaper accounts appeared within hours of the murder. The papers' coverage was based on information provided by the murderer and by Lord Sandwich, both of whom suppressed as much as they revealed. Eighteenth-century newspapers (there were 13 in London and more than 40 in the provinces) relied more on spies, paid informants and interested parties than on reporters. Sandwich, for example, enjoyed a special relationship with the Morning Post. (Its editor had a pension from the king's secret funds.)

So first accounts offered a highly sympathetic telling of the case in which all three protagonists—Sandwich, Ray and Hackman—were portrayed as victims. Sandwich was a reformed rake deprived of the woman he loved, Ray was murdered at the hands of a young man who would not take no for an answer, and Hackman was an upstanding young man driven to a mad act by the power of love. The plot and its characters came right out of the sort of sentimental novel that was being published in huge numbers in the 1770s and in which everyone was a victim.

But after Hackman was executed, his friends went on the offense. They portrayed the perpetrator as a gullible young man lured out of his depth and into a corrupt, high-living world of "lucre, rank and fortune," as Hackman's lawyer, Mannaseh Dawes, put it in his Case and Memoirs of the late Rev. Mr. James Hackman. It was a world where Sandwich and then Ray—"a capricious and an ungrateful woman"—misled Hackman, leading him on to his terrible crime. The story of Hackman's crime became an indictment of the political and social world inhabited by the earl and his mistress and, by extension, of the prosecution of the fratricidal conflict with America. As one journal put it, "Illicit love now reigns triumphant, pervading all degrees, from the peer...to the peasant."

Within a year of Ray's death, a London bookseller, well known for his support of the Americans' cause and his opposition to the government that Sandwich served so ardently, published a book entitled Love and Madness: A Story Too True, which claimed to be the correspondence of the murderer and his victim. In it, Hackman is cast as a romantic hero struggling with the demons of love. Love and Madness quickly became a bestseller and remained in print into the 19th century. But the book was a fake. In fact, the letters were the work of a journalist, Herbert Croft, who deftly recast a story that actually had many actors and intertwined plots into one with a sole tragic protagonist: Hackman. Most readers didn't seem to care that the letters weren't real. The book was hugely influential and helped enshrine Hackman in medical literature as an exemplary case of erotomania, or love's madness.

In the victorian era the story changed yet again. A succession of memoirs and letters of 18th-century life (the most famous were those of Horace Walpole) included accounts of Ray, Hackman and Sandwich. Reviewers and critics pounced on the threesome as typical of the depravity of the Georgian age, what the novelist William Makepeace Thackeray called its "awful debauchery and extravagance." In these, Hackman had become an assassin, Ray a wretched whore, Sandwich a public disgrace. From the vantage point of the mid-19th century, the story exemplified 18th-century wickedness, as well as evidence of the moral progress that had been made in the intervening years. As one reviewer smugly wrote in the Edinburgh Review about the memoirs of George Selwyn, the notorious 18th-century gossip, "We are happy to say that the comparison, suggested by these volumes, between the manners and morals of the last century and our own, is highly satisfactory."

By the end of the 19th century the three lovers had been resurrected by Gilbert Burgess' The Love Letters of Mr. H and Miss R 1775-1779. This bowdlerized and edited version of Croft's Love and Madness was presented as a collection of historical documents. Critics applauded it as "natural and credible," extolling "the awful eloquence which bursts out of supreme human anguish when the victim tries to temper his pain with expressing it."

Finally, in the 20th century, female authors were able to draw on Burgess' "documents" to write the history of the crime from Martha Ray's point of view. They explored the moral dilemma of a woman tied by her children and her poverty to a rich keeper but who, it was supposed, genuinely loved a far more attractive, if impecunious, young man.

Every age, it would seem, rewrote the story for its own purposes. The stern Victorian condemnation of the love triangle is based on the same evidence as the sympathetic accounts written in the 18th century. The differences in motive and moral stance stem only from the larger narrative framework.

So where does the truth lie? I have to confess I do not know. Rereading the many versions, I find none totally convincing; at the same time, all lack the evidence a historian needs to offer an alternative narrative. I suspect, however, that the love triangle was more complicated (and messy) than the historical record implies. The "truth" will probably never be revealed, not least because early efforts to suppress it were so successful.

But the manner in which the story of the three lovers has been told gives us a different sort of insight. It shows how changing values and attitudes continue to shape our perceptions of the past. Who knows, the 21st century may yet yield its own, radically different interpretation. For now, however, the most widely cited version of the "truth" remains Herbert Croft's entirely fictional Love and Madness. Its enduring appeal lies in its powerful evocation of the snares and pitfalls of obsessive love that claimed three victims outside the Covent Garden Theatre on a sultry spring night in 1779.