Michael Morley - The Venice conspiracy

Valentina and Vito follow her, wondering why she didn't just turn the print around. 'You have to stare beyond all the bolder images and look to the background. The artist's first pass on the canvas is Giovanni's 1730 "The Grand Canal and the Church of the Salute", probably his most recognisable work, it's been reproduced in prints and postcards all over the globe.'

She dips down low, like a surveyor checking levels. 'Very good. Actually, it's very, very good.' She traces above the print with her fingers. 'See here – this is the mouth of the canal, there are gondolas in the foreground, but look closely at them and you'll see he's fashioned them from blackened corpses. No doubt an allusion to the Plague. Then we have waterfront houses on the right and the dome of the Salute on the left, like a glimpse of a pale breast, perhaps Mother Venice dying.'

Vito doesn't like the comparison; he wishes the woman was less jovial and indelicate. 'And these?' he asks. 'What do all these cubes and rectangular shapes over the top of things mean?'

Gloria nods. 'Violence. Passion. Aggression. That's what they mean. Some kind of explosion, a release of tension and anger. You can feel the potency pouring off the painting.'

Valentina remembers part of the lengthy briefing they were given by the FBI. 'Are the shapes anything to do with Da Vinci and…' she hesitates for fear of sounding stupid '… Golden Ratios, Golden Rectangles?'

Gloria looks impressed. She tilts her head back and forth at the work. More tracing with her hand, but it's done so quickly, neither of the officers can follow her finger lines. 'You're absolutely right. How clever.' She grabs Valentina's hand and uses her finger like a stick. 'Look here!' Gloria slowly traces the face of a man in profile. 'This is Da Vinci's famous black-and-white illustration from De Divina Proportione – his illustrations here, the way he overlaid the rectangles to show the symmetry of the face, led scholars to speculate that he used the Golden Ratio to create the bewitching magic in the Mona Lisa.' She looks up at the puzzled detectives and hopes they're catching enough of her drift for it to be of use. 'Certainly Dali used it all the time, especially in The Sacrament of the Last Supper, and if you look here you notice symbols from that work too.'

Again Vito and Valentina struggle to see what she's referring to. Gloria places Valentina's finger on the spot. 'Here, in the very middle, we have outstretched hands and the chest of a man hovering against Canaletto's skyline, as if he is ascending to heaven; that godlike figure is from The Last Supper.' She drags Valentina's hand to the left and right of the canvas. 'And here and here you see what look like lop-sided pentagrams; they are also from the backdrop of The Supper.' Gloria stares and sees something new, her face lighting up like a child discovering a final present hidden way back under a Christmas tree. 'Oh, how clever. Clever and awfully crude at the same time.' She addresses Vito. 'Your artist has actually put a tiny gold border all around the outside of the canvas – it isn't obvious on the print, but I suspect it is immensely vibrant on the original work – it acts as a none-too-subtle proclamation that the canvas is a perfect rectangle, a Golden Rectangle, as your officer here said.' She smiles at Valentina, still holding her hand, and squeezing it with a touch of discomforting affection. 'Now, let me see…' Gloria bends so close to the print that her nose virtually touches it. 'Yes! Yes! Here it is-' She slowly slides Valentina's fingers over the print. 'He's divided the work in exactly the way the Golden Ratio dictates. He's created three individual sections, but together they form one overall scene.' This time Gloria touches the print and turns it sideways with her free hand. 'Inventive. He's been truly inventive. The first section shows multiple symbolism, a classic horned demon face, so we can take this to be his bad side. The second looks like a wizard of sorts, I'm not sure of that, and the third seems to be a family scene, lovers alone and at peace with their baby.' She looks Valentina straight in the eyes. 'He's pointing out the good and bad in us all, the light and dark that rule us, perhaps also the dangers that are presented to traditional family life in our day and age.'

Before Vito and Valentina can say anything Gloria spins the print upside down. 'Aah, just as I thought, he's also worked the canvas from the other side. He's very economical, quite prestigious in his canvas coverage.'

Valentina manages to free her hand as Gloria bends closer and stares at some faint detail. 'Now that's odd. Very odd. He seems to have marked each section with Roman numerals. Why should he do that?' Gloria looks to the others for inspiration but they're drawing blanks as well. She points them out: 'Look, in the first of his three sections he's put the numerals XXIV and VII. In the second, the numerals XVI and XI. And in the third section V and VII.'

'What do they mean?' asks Vito. 'Do they have some artistic relevance?'

Gloria shakes her head slowly. 'None. None that I can think of. How strange. Perhaps it's some kind of personal irony. Artists often paint hidden jokes into their works, it gives them a secret thrill.' She can tell from their faces that this notion doesn't appeal to them. She checks her watch. 'I'm sorry, I really have to go. I hope my little critique has been of some assistance.' She fixes her eyes on Valentina. 'Do call me again if you want help. Or if you'd like to go for a drink, or visit a gallery together.'

Vito prevents further embarrassment. 'You've been enormously helpful. We're very grateful. Thank you for taking the time to come. Molte grazie.' He shows her to the door and leaves Valentina staring at the print. She doesn't have Gloria's expert eye, but she can see that the canvas is meant to be more of an abstract message board than a work of art.

'So, what did you make of these numerals?' Vito asks on his return.

'They're not only numbers,' says Valentina, peering closely at the sequences. 'They're a code of some kind.'

Vito looks tired. 'I'd expect it to be a code, but what does it mean and to whom is the code being sent?'

'Now you're asking too much of me,' says Valentina. 'I'll have this copied and sent to the cryptanalysis unit in Rome.' She backs up from the print. 'With a little luck, we may get an answer before the end of the century.'

7th June San Quentin, California Through the toughened glass he sees them change shifts. Both guards check their wrist watches then, in sync, turn their heads towards his cell. What a pair of morons. They don't have an atom of individuality between them.

It's exactly midnight.

The first second of the new day ticks away. The sixth day of the sixth month. Execution Day. His last day on earth.

A time to turn most prisoners' bowels to water.

But not Bale's.

Lars Bale's bowels are just fine and dandy. In fact, he looks a picture of perfect health as he stands in his regulation grey shorts in the middle of his cell, his skin showered in a never-dimmed light that's the colour of mustard gas.

He smiles at the guard clocking off, going home to his undoubtedly inadequate wife sitting up and reading in bed. Waiting for him. He'll tell her about the difficulties of his dull day and then try to be nonchalant as he mentions the most famous moment of his uneventful life – running the Lars Bale death watch on the evening before his execution. He'll tell the story time and time again: in cheap, eat-all-you-can diners, boring family reunions and out-of-town bars. He'll tell it to buddies and complete strangers – and each time the story will get juicier and juicier.

Arms extended, Bale stretches and feels energy flowing from deep within.