Mint tea was served. I jumped straight in and asked Philadelphion if he had had any success with identifying the leaves Theon ate.

‘I consulted a botanist, Falco. His tentative identification is oleander.’

‘Poisonous?’

‘Very’

Helena Justina sat up. ‘Marcus, the garlands!’ She explained to Philadelphion: ‘Our host, Cassius, had special garlands made for the dinner party; they had oleander wound in them.’ She must have noticed the varieties; I can’t say I did at the time.

Philadelphion raised his eyebrows in an elegant gesture. ’My colleague told me it would certainly be possible to murder someone with this plant, though you would somehow have to persuade them to ingest it. He thought the taste would be very bitter.’

‘Try it?’

‘Not brave enough! Taken in sufficient quantities - not unmanageable amounts - it acts within an hour. It works well. I am told it is a favourite choice of suicides.’

‘Was Theon’s dinner garland found with his body?’ I asked.

Philadelphion shook his head. ’Perhaps - but not sent to the necropsy.’

‘Someone cleaned up Theon’s room and may have thrown it out. Know anything about that?’ Again he signalled a negative.

I could see one flaw. Neither Theon, if he felt despairing, nor a potential murderer could have known in advance what foliage would be in our garlands. Cassius had made his selection only the afternoon before the dinner. ‘Would Theon know anything about plants? Would he recognise these leaves or be aware of their toxicity?’

‘He could have looked them up,’ Helena pointed out. ‘After all, Marcus, the man did work in the world’s most comprehensive library!’

‘We have botany and herbal sections,’ confirmed the Zoo Keeper, favouring my wife with one of his very handsome smiles. Unlike Theon, I decided, he was a ladies’ man. Leaving the wife back home in the village must have advantages.

I stretched my legs and asked about that morning’s meeting. ‘You are not the only expert with surgical implements, Philadelphion! Your colleagues had the knives out a few times at the academic board.’

‘They were on good form,’ he agreed, settling down as if he enjoyed gossip. ‘Philetus has a good grasp of essentials - essential being defined by him as that which enhances his own grandeur. Apollophanes devotedly seconds whatever Philetus thinks, regardless of how low it makes him look. Nicanor, the Head of Legal Studies, hates their ineptitude, but is always too wily to say so. Our astronomer has his head in the stars in more ways than one. I try to maintain balance, but it is a lost cause.’

In view of how scathing he had just been, that last comment should have been ironical. Philadelphion failed to see his own bias, and was not one for self-mockery.

‘What was Theon’s usual role?’

‘He argued with Philetus, particularly recently’

‘Why?’

Philadelphion shrugged, though gave the impression he could have made a good guess. ‘Theon started to seize upon pretty well every subject that came up, as if he wanted to disagree with Philetus on principle. I would imagine he had told Philetus what his grievance was. But unlike most of us, who tend to seek support in numbers at the board, he would approach Philetus privately.’

Helena said, “He spoke to us of his regret that the Director was viewed as his superior even though he, Theon, held such a famous post.’

‘Call it more than regret!’ Now Philadelphion was more frank. ’We are all senior men and loathe bending the knee to Philetus, but for the Librarian it is bitterly galling. A previous Director of the Museion - Balbillus, who was in post about ten years ago - took it upon himself to have his title expanded to include oversight of the united Alexandrian libraries.’

‘He sounds Roman?’ I suggested, narrowly.

‘An imperial freedman. Times have changed since the Ptolemies,’ Philadelphion acknowledged. ‘Once, the post of Librarian was a royal appointment, and not just that - the Librarian would be the royal tutor. So originally the Librarian had prestige and independence; he was called ‘The President of the King’s Library’. Through schooling his royal charges, he could become a person of great political influence, too - effectively chief minister.’

I could see why the Roman Prefecture would want to change that. ‘Knowing how things had worked in the past, Theon felt he had been deprived of status.’

‘Exactly, Falco. He suspected he was not taken seriously enough, either by his colleagues here - chiefly by Philetus - or even by your Roman authorities. Forgive me; I cannot put that more delicately’

It was my turn to shrug. ‘As far as Rome goes, Theon did himself down. The Great Library of Alexandria carries enormous prestige in Rome. Its Librarian is automatically held in reverence - which I can assure you the Prefect of Egypt upholds.’

The Zoo Keeper appeared not to believe me. ‘Well, his reduced position was a long-standing grievance. It wore him down. And I believe there was administrative friction too.’

Since he had nothing to add, we moved on. ‘I gained a good impression of Timosthenes at the meeting - he is in charge of the Serapeion, isn’t he?’ Helena asked. I won’t say she thought I was flagging, but she lifted her stole over her shoulder and smoothed down her shimmering summer skirts like a girl who has decided it is her turn.

‘Up on the hill, over towards the lake. It is a complex devoted to Serapis, our local “synthetic” deity.’

‘Synthetic? Someone deliberately invented a god?’ Privately, I thought it must have made a change from counting the legs on millipedes and producing geometry theorems. ‘Tell us!’ Helena prompted, apparently as full of glee as our girls had been at the crocodile pit.

I doubted he approved of formal female education, but Philadelphion liked lecturing women. Folding her hands in her lap, Helena tipped her head on one side so a gold ear-ring tinkled faintly against her perfumed neck as she encouraged him shamelessly. ‘Noble lady, this was a deliberate attempt by the Ptolemy kings to conjoin the ancient Egyptian religion with their own Greek gods.’

‘Far-sighted!’ Helena’s clear smile included me. She knew I was exuding bile.

Philadelphion apparently missed the moment between us. ‘They took the Apis bull from Memphis, who represents Osiris after death, and created a composition with various Hellenistic deities: a supreme god of majesty and the sun - Zeus and Helios. Fertility - Dionysos. The Underworld and afterlife - Hades. And healing-Asklepios. There is a sanctuary, with a superb temple - and also what we call the Daughter Library. Timosthenes can tell you the exact arrangements, but it takes scrolls for which there is no room at the Great Library; duplicates, I imagine. The rules are different. The Great Library is only open to accredited scholars, but the Serapeion can be used by members of the public.’

‘I imagine some scholars look down on public access,” I suggested. ‘Timosthenes’ ideas for open lectures were quickly shouted down at the board meeting.’ Philadelphion produced one of his airy shrugs. I did not have him down as a snob and I thought he was just avoiding controversy.

Time was pressing. Helena gave me one of those meaningful looks that husbands are taught by their wives to act upon. We could not abandon our two infants for much longer; it was unfair both on Albia and the zoo staff. But Philadelphion was in a good mood to talk. As the race for Theon’s post hotted up, such a moment might not happen again, so I slipped in a last question: ‘Tell me who is in the running for this shortlist for the librarianship. I presume you yourself must be a favourite?’

‘Only if I can keep myself from wringing the Director’s neck,’ Philadelphion admitted, his tone still pleasant. ‘Apollophanes thinks he will walk away with the prize, but he has no seniority and his work lacks prestige. Aeacidas - whom you may have noticed yesterday, Falco - is pushing to be considered, on the grounds that literature is the most relevant subject.’