“Fabulous!” Kenneth restlessly offered. “Psychedelic, aren’t they?”

Grant disregarded this. He said to Sophy: “He’s so very doubtful, isn’t he? Head on one side, lips pursed up and those gimlet fingers! How right that enormous hospital in London was to adopt him: he’s the very pith and marrow of the scientific man, don’t you think?”

Sebastian Mailer gave a shrill little cackle of appreciation, perhaps of surprise.

“While we are in this aisle of the basilica,” Grant said, leading them along it for a short distance, “you may like to see something that I’m afraid I did adopt holus-bolus.”

He showed them a railed enclosure, about six feet by three in size. They collected round it with little cries of recognition.

It encompassed an open rectangular hole like the mouth of a well. Fixed to the rails was a notice saying in five languages that climbing them was strictly forbidden.

“Listen,” Grant said. “Can you hear?”

They stood still. Into the silence came the desultory voices of other sightseers moving about the basilica, the voice of a guide out in the atrium, footfalls on marble and a distant rumour of the Roman streets. “Listen,” Grant repeated, and presently from under their feet, scarcely recognizable at first but soon declaring itself, rose the sound of running water, a steady, colloquial voice, complex and unbroken.

“The cloaca maxima?” Major Sweet demanded.

“A pure stream leading into it,” Grant rejoined. “More than sixty feet below us. If you lean over the rail you may be able to see that there is an equivalent opening immediately beneath this one, in the floor of the earlier church. Yet another thirty feet below, out of sight unless someone uses a torch, is a third opening, and far down that, if a torch is lowered, it’s possible to see the stream that we can hear. You may remember that Simon dropped a pebble from here and that it fell down through the centuries into the hidden waters.”

The Van der Veghels broke into excited comment.

Grant, they warmly informed him, had based the whole complex of imagery in his book upon this exciting phenomenon. “As the deeper reaches of Simon’s personality were explored—” on and on they went, explaining the work to its author. Alleyn, who admired the book, thought that they were probably right but laid far too much insistence on an essentially delicate process of thought.

Grant fairly successfully repressed whatever embarrassment he felt. Suddenly the Baron and Baroness burst out in simultaneous laughter and cries of apology. How ridiculous! How impertinent! Really, what could have possessed them!

Throughout this incident, Major Sweet had contemplated the Van der Veghels with raised eyebrows and a slight snarl. Sophy, stifling a dreadful urge to giggle, found herself observed by Alleyn and Grant, while Lady Braceley turned her huge, deadened lamps from one man to another, eager to respond to whatever mood she might fancy she detected.

Kenneth leant far over the rail and peered into the depths. “I’m looking down through the centuries?” he announced. His voice was distorted as if he spoke into an enormous megaphone. “Boom! Boom!” he shouted and was echoed far below. “Ghost beneath: Swear,” he boomed and then: “Oh God!” He straightened up and was seen to have turned a sickly white. “I’d forgotten,” he said. “I’m allergic to heights. What a revolting place.”

“Shall we move on?” said Grant.

Sebastian Mailer led the way to a vestibule where there was the usual shop for postcards, trinkets and colour slides. Here he produced tickets of admission into the lower regions of San Tommaso.

The first descent was by way of two flights of stone stairs with a landing between. The air was fresh and dry and smelt only of stone. On the landing was a map of the underground regions and Mailer drew their attention to it “There’s another one down below,” he said. “Later on, some of you may like to explore. You can’t really get lost: if you think you are, keep on going up any stairs you meet and sooner or later you’ll find yourself here. These are very beautiful, aren’t they?”

He drew their attention to two lovely pillars laced about with convolvulus tendrils. “Pagan,” Mr. Mailer crooned, “gloriously pagan. Uplifted from their harmonious resting place in the Flavian house below. By industrious servants of the Vatican. There are ways and ways of looking at the Church’s appropriations, are there not?”

Major Sweet astonished his companions by awarding this remark a snort of endorsement and approval.

Mr. Mailer smiled and continued. “Before we descend — look, ladies and gentlemen, behind you.”

They turned. In two niches of the opposite wall were terra-cotta sculptures: one a male, ringletted and smiling, the other a tall woman with a broken child in her arms. They were superbly lit from below and seemed to have, at that instant, sprung to life.

“Apollo, it is thought,” Mr. Mailer said, “and perhaps Athena. Etruscan of course. But the archaic smiles are Greek. The Greeks, you know, despised the Etruscans for their cruelty in battle and there are people who read cruelty into these smiles, transposed to Etruscan mouths.” He turned to Grant: “You, I believe—” he began and stopped. Grant was staring at the Van der Veghels with an intensity that communicated itself to the rest of the party.

They stood side-by-side admiring the sculptures. Their likeness, already noticed by Grant, to the Etruscan terra-cottas of the Villa Giulia startlingly declared itself here. It was as if their faces were glasses in which Apollo and Athena smiled at their own images. Sharp arrowhead smiles, full eyes and that almost uncanny liveliness — the lot, thought Alleyn.

It was obvious that all the company had been struck by this resemblance except, perhaps, Lady Braceley, who was uninterested in the Van der Veghels. But nobody ventured to remark on it apart from Sebastian Mailer, who with an extraordinary smirk murmured as if to himself: “How very remarkable. Both.”

The Van der Veghels, busy with flashlights, appeared not to hear him and Alleyn very much doubted if any of the others did. Barnaby Grant was already leading them down a further flight of steps into a church that for fifteen hundred years had lain buried.

In excavating it a number of walls, arches and pillars had been introduced to support the new basilica above it. The ancient church apart from the original apse was now a place of rather low, narrow passages, of deep shadows and of echoes. Clearly heard, whenever they all kept still, was the voice of the subterranean stream. At intervals these regions were most skillfully lit so that strange faces with large eyes floated out of the dark: wall paintings that had been preserved in their long sleep by close-packed earth.

“The air,” Barnaby Grant said, “has done them no good. They are slowly fading.”

“They enjoyed being stifled,” Sebastian Mailer said from somewhere in the rear. He gave out a little whinnying sound.

“More than I do,” Lady Braceley said. “It’s horribly stuffy down here, isn’t it?”

“There are plenty of vents,” Major Sweet said. “The air is noticeably fresh, Lady Braceley.”

“I don’t think so,” she complained. “I don’t think I’m enjoying this part, Major. I don’t think I want—” She screamed.

They had turned a corner and come face-to-face with a nude, white man wearing a crown of leaves in his curls. He had full, staring eyes and again the archaic smile. His right arm stretched towards them.

“Auntie darling, what are you on about!” Kenneth said. “He’s fabulous. Who is he, Seb?”

“Apollo again. Apollo shines bright in the Mithraic mystery. He was raised up from below by recent excavators to garnish the Galalian corridors.”

“Damn’ highfalutin’ poppycock,” Major Sweet remarked. It was impossible to make out in what camp he belonged. So Kenneth, Alleyn noted, calls Mailer “Seb.” Quick work!