She strolled down the rue Leffinge and turned left on the Chaussee de Thourout, lifting her face to the mild sun, deliberately not thinking about the day ahead, trying to pretend she was a young Belgian woman – like the other young Belgian women she saw on the street about her – a young Belgian woman going about her business in a small town in a small country in a world that made some sort of sense.

She turned right at the clock tower and crossed the small square towards the Cafe de Paris. She thought about stopping for a coffee but realised that Sylvia would be waiting impatiently to be relieved from the night shift and so strode briskly onwards. At the tram depot she saw on the billboards the fading posters from last summer's races – Le Grand Prix Internationale d'Ostende 1939 – strange reminders from a world that was then at peace. She turned left at the post office into the rue d'Yser and immediately saw the new sign Romer had had installed. Royal blue on lemon yellow: Agence d'Information Nadal – or, as Romer preferred to call it: 'The Rumour Factory'.

The building was a 1920s three-storey rectilinear office block, with a curved, pillared porte-cochere over the main entrance, in austere Streamline Moderne style, an effect which was rather undermined by the decorative pseudo-Egyptian frieze that ran under the simple cornice of the top floor. On the roof was a thirty-foot wireless transmitter tower, like a mini-Tour Eiffel, painted red and white. It was this, rather than any architectural pretensions, that made the odd passer-by offer the building a second glance.

Eva walked in, nodded to the receptionist, and climbed the stairs to the top floor. The Agence d'Information Nadal was a small news agency, a minnow compared to the giants like Reuters, Agence Havas or Associated Press but which did, essentially, the same job – namely sell news and information to various customers unprepared or unable to gather that news and information themselves. A.I. Nadal serviced some 137 local newspapers and radio stations in Belgium, Holland and northern France and made a modest but steady profit. Romer had bought it in 1938 from its founder Pierre-Henri Nadal, a spruce white-haired old gent who wore co-respondent shoes and a boater in summer and who occasionally popped in to the office to see how his child was progressing under the new foster-parents. Romer had kept the essentials and discreetly added the modifications he required. The radio tower was heightened and made more powerful. The original staff, some dozen Belgian journalists, were retained but quartered on the second floor, where they continued to sift and disseminate the local news from this small corner of northern Europe – livestock sales, village fetes, bicycle races, high and low tides, closing prices from the Brussels bourse and so on – duly passing their copy down to the telegraphists on the ground floor, who transformed the information into Morse code and telegraphed it to the agency's 137 subscribers.

Romer's unit occupied the third floor. A small team of five who spent their days reading every European and relevant foreign newspaper they could find, and who, after due process of consultation and discussion, would insert, from time to time, a particular Romer-story into the mass of trivia beamed out from the innocuous building on the rue d'Yser.

Apart from Romer and Eva the other four members of Romer's 'team' were Morris Devereux – Romer's number two – an elegant and suave ex-Cambridge don; Angus Woolf, a former Fleet Street journalist who was severely crippled by some congenital deformation of his spine; Sylvia Rhys-Meyer – Eva's flatmate – a lively woman in her late thirties, married and divorced three times and an ex-Foreign Office linguist and translator; and Alfie Blytheswood – who had nothing to do with the material that came out of the agency but was responsible for the maintenance and smooth running of the powerful transmitters and the occasional wireless encryptions. This was AAS in its entirety, Eva came to realise, very quickly: Romer's team was small and tight-knit – apart from her everyone seemed to have been working for him for several years, Morris Devereux even longer.

Eva hung her coat and hat on her usual hook and made for her desk. Sylvia was still there, flicking through yesterday's Swedish newspapers. The ashtray in front of her was brimful of cigarette butts.

'Busy night?'

Sylvia arched her back and eased her shoulders to simulate fatigue. She looked like a stout, no-nonsense county wife, the wife of the local GP or a gentleman farmer, bosomy and broad-hipped, who wore well-cut suits and expensive accessories – except that everything else about Sylvia Rhys-Meyer contradicted that initial assessment.

'Fucking boring, fucking dull boring, boring dull fucking, dull fucking boring,' she said, standing up to allow Eva to take her seat.

'Oh, yes,' Sylvia added. 'Your dead-sailors piece has been picked up all over the place.' She opened and pointed to a page in the Svenska Dagbladet. 'And it's in The Times and in Le Monde. Congratulations. His nibs will be very pleased.'

Eva looked at the Swedish text, recognising certain words. It was a story she had suggested at conference a few days before: the idea of twenty Icelandic sailors washed up in a remote Norwegian fjord, alleging that their fishing boat had sailed into heavily mined waters off the port of Narvik. Eva knew at once that it was the sort of story Romer loved. It had already provoked an official denial by the British War Office (Norwegian territorial waters had not been mined by British ships) – more to the point, as Romer would say, it was loose intelligence: a fishing boat sunk by a mine – where? – and it was information useful to the enemy. Any further denials would be either disbelieved or be too late – the news was out there in the world doing its dirty work. German intelligence officials monitoring the world's media would note the alleged presence of mines off the Norwegian coast. This would be conveyed to the navy; maps would be taken out, amended, altered. It was, in essence, the ideal illustration of how Romer's unit and A.I. Nadal was meant to work. Information wasn't neutral, Romer constantly repeated: if it was believed or even half believed, then everything began subtly to change as a result – the ripple effect could have consequences no one could foresee. Eva had had previous small successes during the four months she'd been in Ostend – news of imaginary bridges being planned for, of Dutch flood defences reinforced, of trains being re-routed in northern France because of new military manoeuvres – but this was the first time the international press had picked up one of her stories. Romer's idea, like all good ideas, was very simple: false information can be just as useful, influential, as telling, transforming or as damaging as true information. In a world where A.I. Nadal fed 137 news outlets, twenty-four hours a day, 365 days a year, how could you tell what was genuine and what was the product of a clever, devious and determined mind?

Eva took her seat, still warm from Sylvia's generous buttocks, and pulled a pile of Russian and French newspapers towards her. She assumed that someone high up in the British Secret Service had seen the merit in Romer's idea and that this explained the strange autonomy he seemed to possess. It was the British taxpayer, she surmised, who had bought the Agence d'Information Nadal (and thereby ensured Pierre-Henri Nadal a very comfortable retirement) and was now funding its development as part of its Political Warfare department. Romer and his 'unit' were involved in feeding careful and clever false information out into the world – through the bona-fide medium of a small Belgian press agency – and nobody really knew what the effect might be. No one could tell if the German high command was taking note, but the unit always counted it a success if their stories were picked up (and paid for) by other newspapers and radio stations. However, Romer seemed to want the stories they sent out to conform to some kind of plan to which only he had the key. In conference, he would sometimes demand stories about rumours of potential resignations of this or that minister, or scandals undermining this or that government; or he would say, suddenly: we need something on Spanish neutrality; or else call immediately for statistics about the increase in sheet-metal production in French foundries. The lies had to be constructed with all the scrupulousness of truth. Instant plausibility was the key concern – and the team laboured to supply it. But it was all somewhat vague and all – to tell the truth as Eva saw it – something of a parlour game. They never knew the consequences of their clever little fibs: it was as if the individual members of the unit were players in an orchestra, sequestered in soundproof rooms – only Romer was able to make out the harmonies of the tune they were playing.