' – I'm pretty sure that the Aishlie cup lapsed in 1930 or 1931,' he was saying. He smiled at me, toothily. 'I've only been here three years.'

Carriscant pushed his photograph across the desk. 'This is the woman we are interested in. She was the wife of an embassy official here, I'm sure.'

Dillingham looked attentively at the picture. 'Very elegant lady,' he said. 'What age would she be there?'

'Early fifties.'

'Let me see.' He went to his bookshelf and drew out a slim navy blue book from a row of identically bound volumes. On the cover was a gold seal and lettering that read: Department of State, Foreign Service List, 1927. He flicked through the pages.

'The envoy in 1927 was Warrick Aishlie and we know that the lady in question is not Mrs Aishlie… The only other diplomats of an age to have a wife in her fifties are…'

He consulted the list. 'Hmm. Mr Parker Gade, vice consul in Funchal, and Commander Mason Shoemaker, the naval attache for air.' He made an impressed noise. 'That was forward looking for us in 1927. Now,' he reached for the 1936 service list, 'let's see where they are today.'

'Naval commander?' Carriscant said, drawing the photo back. 'Could that be him in the picture?'

'I couldn't tell you, sir,' Dillingham said as he checked the index. 'No reference. Both of these gentlemen appear to have retired from the service. Or they're deceased.' He made an unhappy face. 'I could cable the State Department, but I'm fairly sure they wouldn't give out any personal information.'

Carriscant suddenly looked glum and unhappy, shifting uncertainly in his seat, his fingers tugging at the collar of his new shirt, and I felt sorry for him, his hopes raised and dashed so swiftly.

'Isn't there anyone here in the legation who was here in 1927?' I asked. 'There must be some member of staff who goes back that far.'

'Good point,' Dillingham said, throwing me an admiring glance. 'Please excuse me one moment.'

Carriscant stood up and went to the window to look down on the little courtyard outside. I joined him. Some small scruffy pigeons pecked around the base of a lime tree, pecking in a dilatory and routine manner at the sparse blades of grass, as if the search for nourishment itself was sufficient to satisfy their hunger.

'If she did marry this naval commander she could be anywhere,' I said gently.

'No,' Carriscant said with complete confidence. 'She's here, I'm certain of it.'

I turned away, exasperated. He had all the doggedness of a Flat-Earther. These people had to find out the hard way.

Dillingham returned with an elderly Portuguese man in a black suit. He had grey hair combed brutally back from his forehead and held in place with some fearsomely adhesive grease or potion. He wore small round tortoise-shell glasses and a neatly trimmed toothbrush moustache dyed a disconcerting shade of coppery brown.

'Senhor Liceu,' Dillingham said, presenting him. 'Our esteemed chancery clerk. Been here for ever.'

Senhor Liceu shook hands with us, inclining his trunk forward at a slight angle each time. Carriscant showed him the photograph and asked if he could identify Commander Shoemaker.

He did so at once. 'That's Commander Shoemaker,' he said. 'A good likeness.' His English was excellent.

Carriscant pointed to Delphine. 'And is that Mrs Shoemaker?'

Liceu tried not to smile at some memory. 'No, sir, there was no Mrs Shoemaker. The commander was a confirmed bachelor.'

'Do you recognise that lady?'

'No, I'm afraid not. I was there that day, I remember it well. I was a great admirer of Senhorita Barrera.' He gave a sad smile. 'I think I only had eyes for her. This lady was probably Commander Shoemaker's guest. Or Mr Aishlie's.' Despair was creeping back into Carriscant's face. 'Could this lady have been French?' Liceu said, frowning. 'I have some recollection of a very elegant French lady at one of the receptions.'

'I don't think so.' Carriscant shrugged. 'Unless she married a Frenchman.'

'I'll ask some of the other staff,' Liceu volunteered. 'Perhaps someone will remember. It was a great day for the legation. Most memorable. There may be others with better recall than I.'

We thanked them both and left the place somewhat cast down. We walked down the front steps slowly. Evening was coming on and the streetlamps were lit. In the sky above were a few pink-touched clouds. A taxi pulled up and a young man with bad acne descended and spent some time searching his pockets for change while the taxi ticked patiently at the kerb. I felt Carriscant's depression settle round my shoulders like a shawl. I had to say something.

'How does it go? "At the violet hour, something something, like a taxi throbbing at the door"… No, "the human engine, like a taxi throbbing at the door".'

'What on earth are you talking about?' Carriscant rather snapped at me.

'Just a line of poetry. Came to mind. "At the violet hour, etcetera".' I pointed up at the rose-flushed evening sky. 'It's nothing important. Just the conjunction of the light effect and that taxi. Ignore it.'

He was staring at me, a slow smile widening his face. 'At the violet hour,' he said. 'Don't you see?'

'What? No, I don't.'

'Violets.'

FRIDAY, 5 MAY

We spent the morning walking round the Baixa going from sweetshop to sweetshop looking for one that sold crystallised violets. Out of six confeiteiros we found only one with a stock of the sweets. We returned with Joao from the hotel to help us translate.

'They sell many types of sweets,' Joao said needlessly as we looked round the small shop. It was narrow and dark and looked more like an apothecary's with its crammed shelves of ornate glass bottles, some of them tinted green and blue. 'But they have no regular order for the violets. They do not despatch them to special clients.'

'What about regular customers?'

Joao conferred with the bemused couple who ran the shop. Yes, they did have some regular customers. They peered curiously at Carriscant's picture. No, they didn't recognise the woman.

Undeterred, Carriscant secured the name of the wholesaler who supplied them with the sweets; from him he would obtain a list of other stockists in the city, he explained.

I was beginning to grow a little worried. If ever there was an example of clutching at straws… But Carriscant persisted, extracting a promise from them that they would ask anyone who bought the sweets to provide their name and address. They would try, they said, obviously affected by the earnestness of Carriscant's demand, but they warned that not everyone would be prepared to divulge that information.

We found a small cafe nearby, the Cafe Adamastor, and stopped there for refreshment. It was little more than a smoke-darkened room with a long zinc-topped bar running the length of the rear wall with a shelf above ranged with small dumpy barrels, with spigots attached, labelled Moscatel, Clarete, Ginebra. Fixed to the ceiling was a small fan mounted vertically on the end of a hanging pole so that it resembled a propeller shaft on an outboard motor. This revolved slowly round and round, ensuring that the cigarette smoke reached every corner of the room.

We sat at a round marble-topped table. I ordered a vinho verde, Carriscant a brandy. I sipped eagerly at my cold wine, it tasted fresh and young, like crushed grass. I took out my cigarettes.

'I don't think you should do that, Kay.'

'Do what?'

'Smoke.'

'Everyone else is, why not me, for heaven's sake?'

'None of the women are… I have a feeling it's not the done thing.'

'Well, I shall blaze a trail,' I said, defiantly setting fire to my Picayune. Carriscant's instincts were correct, however: I became the object of fascinated stares and whispered conversations for a minute or two.