Tess couldn't help staring toward a clock on the wall. Craig. He'd be landing at Washington National Airport soon! He expected her to meet him!

'Don't look at the clock, Tess. Look at me. Keep paying attention.' Priscilla braced her shoulders with professorial sternness. The concept of opposite but equally powerful gods spread throughout the Mideast. By the time it showed up in ancient Iran, around one thousand BC, the virtuous god had a name. Mithras.'

Tess jerked straighter. 'Mithras? You mentioned him before.'

'Yes. The figure in the bas-relief sculpture,' Priscilla said. 'Now do you understand why I had to go into so much detail? The figure killing the bull is not a man. He's a god. Various later religions, Zoroastrianism and Manichaeism, also used the concept of equal, competing, good and evil gods. But essentially those gods are versions of Mithras and his evil counterpart. We're talking old, Tess. Very old. That's what I meant when I said that Mithras comes from the roots of history. He's the most ancient notion of a god we have any specific knowledge of, and it's only by chance that…'

Professor Harding interrupted, supporting himself with his cane while he wheeled in a cart upon which a teapot, cups, and a plate of biscuits were arranged.

'Thank you, Richard.'

'I'm pleased to help, dear.'

'It's only by chance that what?' Tess asked, impatient for Priscilla to continue.

'Milk, dear?' Professor Harding asked.

'Just a little.'

Tess became more impatient, barely able to restrain herself from telling Priscilla to hurry.

While Professor Harding poured the tea, Priscilla pensively opened one of the books she'd set on the desk, leafed through it, and found the page she wanted. 'Let me describe a religion to you. When you enter its church, you dip your hand in a holy-water basin and make the Sign of the Cross. On the altar, you see a representation of the physical form of your God. During the service, you receive a communion of bread and wine. You believe in baptism, confirmation, salvation through good works, and life after death. The physical form of your deity has his birthday on December twenty-fifth, and his rebirth occurs during the Easter season.'

Professor Harding wrapped each steaming teacup with a napkin and handed them to Priscilla and Tess. 'Catholicism,' he said.

'Yes, that would be the logical assumption, Richard. However, with apologies, you're wrong.' Priscilla kept staring at Tess. 'It's Mithraism.'

'What?' Tess set down the teacup and blinked in surprise. 'But how can there be so many parallels? You said that Mithraism came long before Christianity.'

'Think about it.' Priscilla lowered and peered over her glasses. 'I'm sure the answer will occur to you.'

'The only explanation I can… It doesn't seem possible. Christianity borrowed from Mithraism?'

'So it appears,' Priscilla said. 'For the first three centuries after Christ, while Christianity struggled to survive, Mithraism was a major force in the Roman Empire. Several Roman emperors not only endorsed it but were members. Mithras is sometimes called the sun god, and because of him, Sunday assumed sacred importance for the Romans and eventually for Western culture. Mithras is often pictured with a sun behind his head, and that sun became the halo around the heads of major figures in Christian art. The cross, by the way, is an ancient symbol that represents the sun. Thus believers in Mithras made the Sign of the Cross when they entered their church to worship the sun god.'

Priscilla turned the book and slid it toward Tess. 'Here's a photograph of an ancient bas-relief depicting a Mithraic communion service. Notice that the pieces of communion bread have a cross etched into them.'

'Before Christianity?' Tess felt off-balance. 'But this is… All my religious training, everything I took for granted about Catholicism… I feel like I'm sinking.'

'I warned you.' Priscilla raised her swollen fingers. 'I told you that what I had to say might undermine your faith. I tried to prepare you when I said it might be terrifying. In more ways than one. But I'll get to that.'

Professor Harding sipped from his teacup, sighed in appreciation of the taste, swallowed with pleasure, and interrupted. 'My dear…'

'Yes, Richard?'

'When I came in, you said it was only by chance that… What was only by chance?'

'That's what I want to know,' Tess said.

'I meant…' Priscilla narrowed her gaze. 'It was only by chance that Mithraism didn't assume the dominance in Western culture that Christianity now has. As I mentioned, in the first three centuries after Christ, several Roman emperors pledged themselves to Mithras. But all of that changed with Constantine. In the year three-twelve, just before Constantine was about to send his army against his major enemy in the famous battle at the Milvian Bridge, Constantine had what he later described as a vision.'

'Vision?'

'Perhaps it's another myth. Constantine peered toward the sky and claimed that he saw a cross of light imposed on the sun. He interpreted this as a message from God and ordered his soldiers to paint similar crosses on their shields. They entered and won the battle – under the Sign of the Cross. Considering that the cross is an ancient symbol for the sun and that Mithraism favored that symbol as a reference to its sun god, historians aren't clear why Constantine seemed arbitrarily to decide that this cross referred to the crucifix, the cross upon which Christ had died.' Priscilla settled back. 'In any event, Constantine converted to Christianity and eventually made it the primary Roman religion. Christians, who until then had been tolerated at best – when not spurned or thrown to the lions – were quick to take advantage of their sudden influence. Their urgent priority was to stamp out the sect that rivaled them. Mithraic chapels were sought out and destroyed. Mithraic priests were killed, their corpses chained to their altars… to so desecrate the Mithraic chapels that they'd never be used again. The balance of history tilted, and Mithraism abruptly declined. Persecuted as heretics, its few remaining followers went into hiding. In small groups, they performed their rites in secret. But no matter how stringently they were hunted, they managed to survive. In fact, to this day, Mithraism is practised in India.'

Priscilla sipped her tea, gaining strength. 'But in Europe, the last vestige of Mithraism was eradicated during the Middle Ages. In the thirteenth century, the concept of two opposing, equal gods – one good and one evil – surfaced again in a town in southwestern France called Albi. The Catholic Church referred to the name of the town and declared that this unexpected reappearance of Mithraism was the Albigensian Heresy. After all, there could only be one God. The papally authorized crusaders, thousands of them, converged on southwestern France and massacred anyone – multitudes!-whom they suspected of being a heretic. Eventually they forced the supposed disbelievers onto a mountain fortress. Montsegur. There, the crusaders waited until the heretics surrendered due to starvation and thirst. The crusaders then herded the heretics into a wooden stockade, set fire to it, and watched while the heretics burned. That was the last time, more than seven hundred years ago, that a version of Mithraism raised its head in the Western world.'

'But you don't look convinced,' Tess said.

'Well.' Priscilla debated. 'A rumor persists that the night before the massacre, a small group of determined heretics used ropes to descend from the mountain fortress, taking with them a mysterious treasure. I've sometimes wondered if pockets of the heretics might have survived, remaining in hiding to the present day. And the photograph of that sculpture makes me suspect I'm right. It's not as if you can walk into an art gallery that specializes in ancient artifacts and simply buy one of these objects off the shelf. If any were available, the price would be outrageous because, as I told you, most of the bas-relief statues were destroyed after Constantine converted to Christianity. The few that survived are museum pieces. The best two I know of are in the Louvre and in the British National Museum.'