'Do they? Golden Ages have a way of being overrated. And they never seem to last Tell me, is Aratus still the foreman?'

'Yes, and a better one I've never worked for. A steady hand in good times and bad.'

'So he is, and I hope your master appreciates him And tell me, is Congrio still the cook?'

'He was, until shortly after the master inherited the farm. Then the master made Congrio a free man and let him go off to the city with a bag of silver on his belt. Can you imagine that?'

'Yes,' I said, ‘I think I can.'

From this story, you may draw your own conclusions.

Recounting this tale, putting it into words as if you were here, makes me miss you very much, my son. I worry for your safety. I long for your companionship. Though we have had our differences, there are things we two understand that no one else knows o£ and so you are precious to me. Without you, there would be no one else to remember and bear witness to certain incidents that still confound and haunt me.

Seeing the farm again has unleashed many memories, which circle my head like harpies. To whom but you could I ever speak of my feelings about Catilina? What a waste, I sometimes think, to have spent my precious time with him suspecting and resisting him! But another part of me says: What if you had supported him, given yourself to him heart and soul — towards what end? And an even more sceptical part still doubts everything about Catilina and suspects he was nothing more than a very charming and very desperate charlatan, no different from the rest.

To my knowledge there is no god of regret, or of doubt; why should there be when a Roman is not supposed to feel such things? And so there is no altar upon which I can lay these feelings, see them purified by name and turned to ash. Instead I live with doubt and regret, sustained by the love of those close to me, bemused by such ironies as Cicero's exile and Claudia's fate, and I continue to ponder, as I know you must, Catilina's riddle.

Few figures in history have attracted more controversy than Lucius Sergius Catilina. A generation after his death he was already being portrayed as a damned soul by Virgil in the Aeneid. Over the centuries he has alternately been held up as a hero or villain, often in extreme terms. Two works published hundreds of years and thousands of miles apart illustrate the dichotomy by their tides alone: compare Patriae Parricida: The History of the Horrid Conspiracy of Catiline Against the Commonwealth of Rome, published by an anonymous pamphleteer in London in 1683, and Ernesto Palacio's Catilina: Una Revolution contra la Plutocrada en Roma, published in Buenos Aires in 1977. Which is it to be: Catilina the depraved insurrectionist, or Catilina the heroic revolutionary? The destroyer of decency, or the champion of the underclass?

Ben Jonson adhered faithfully to the classical sources hostile to Catilina to produce Catiline his Conspiracy, a tragedy first performed in 1611 by the players of King James and revived in the Restoration; its antirevolutionary themes would please a monarch. Voltaire made Cicero an exemplar for the Age of Reason and Catilina an agent of chaos in his play Rome Sauvie, ou Catilina, which grossly distorts the historical record; Caesar is sent into the field to fight the conspirators! (From Gaston Bossier's La Conjuration de Catilina of1905 we learn that Robespierre was called le Catilina modeme.) In 1850 Ibsen delivered a radical revisionist Catilina which portrays the conspirator as a sort of Hamlet struggling with his conscience to take a stand against tyranny.

'The problem with Catilina lies in the primary sources, which are severely biased against him. Cicero's four famous orations against Catilina are models of invective, and Sallust, who was a partisan of Caesar, had his own agenda when he wrote his book-length history of the Bellum Catilinae. The venom in these accounts must be taken with a grain of salt. One finds evidence from his own writings that before and after the conspiracy Cicero found much to admire in Catilina, and Sallust, while repeating every vile rumour about Catilina and his followers like a dutiful tabloid reporter, nevertheless provides compelling evidence to justify their actions.

Many modern historians seem content to accept the negative portrait of Catilina at face value, even knowing that it was painted by his enemies. Others follow revisionist lines that seek to look behind Cicero's rhetoric and Sallust's melodrama. In general, the clearest revelation to emerge from most historical reconstructions is of the particular historian's personal politics and point of view; Catilina becomes merely a prop. Even more distressing are those historians who insist on having the 'last word' on a subject for which there can be no last word, short of the invention of time travel or communication with the dead.

Fortunately, the first-person novelist, liberated from any pretence of omniscience, can adhere scrupulously to historical evidence even while allowing for the development of a subjective interpretation. The essential details in Catilina's Riddle, including the speeches and the various political manoeuvrings, are authentic. Nevertheless, the reader is ultimately free to question Gordianus's perceptions and his conclusions, as does Gordianus himself. It has not been my aim to rehabilitate Catilina, as Josephine Tey sought to rehabilitate Richard III in The Daughter of Time. Catilina remains today what he must have been in his own time: an enigma, which is to say, a riddle.

Books beget books, and I should acknowledge the one that first made me think that a novel about Catilina was dramatically feasible, The Conspiracy of Catiline by Lester Hutchinson (Barnes and Noble, 1967), which remains my favourite book-length reconstruction. Among shorter works, 'In Defense of Catiline' by Walter Allen, Jr. (Classical Journal 34,1938) provided unique insights. I should also acknowledge Arthur D. Kahn's The Education of Julius Caesar (Schocken Books, 1986); the very title of his chapter 'The Conspiracy of Cicero and Catilina' challenged me to turn every interpretation I encountered inside out.

Among primary sources, after Cicero and Sallust come the Roman histories of Appian and Dio, and of course the Lives of Plutarch, a treasure trove of juicy details, including the use of Tironian shorthand to record the Senate's debate, Cato's altercation with Caesar over Servilia's love letter, and the notorious riddle itself What a pity that Plutarch left us no full-scale biography of Catilina!

Readers of previous novels in the 'Roma Sub Rosa' series, curious about Gordianus's benefactor, Lucius Claudius, may wish to know that he has previously appeared in short stories belonging to the series, most of them published in Ellery Queen's Mystery Magazine.

Research for this novel was conducted at the San Francisco Public Library and through the Interlibrary Loan system; at the Perry-Castaneda Library at the University of Texas in Austin; and at Harvard's Widener Library. For access to the latter I am grateful to Michael Bronski and Walta Borawski.

My personal thanks, as always, to my editor Michael Denneny and his assistant, Keith Kahla; to Penni Kimmel for reading the manuscript; to my sister Gwyn, Keeper of the Disks; and of course to Rick Solomon, Master of the Macintosh and all its mysteries.