The town has been so quiet since you left. It is as if its very spirit left with you. Madame Louvier comes in, perverse to the last, and insists that your name must still be heard. She harangues anyone who will listen. Herr Kommandant is not among the handful of Germans who arrive for their meal in the evening. I truly believe he cannot meet my gaze. Or perhaps he knows I should like to run him through with my good paring knife and has decided to stay away.

Little snippets of information still find their way through: a scrap of paper under my door told of another outbreak of influenza near Lille, a convoy of Allied soldiers captured near Douai, horses killed for meat on the Belgian border. No word from Jean-Michel. No word from you.

Some days I feel as if I am buried in a mine and can hear only the echoes of voices at some distance. All those I love, aside from the children, have been taken away from me and I no longer know whether any of you are alive or dead. Sometimes my fear for you grows so great that I find myself paralysed, and I will be in the middle of stirring some soup or laying a table and I have to force myself to breathe, to tell myself I must be strong for the children. Most of all, I must have faith. What would Sophie do? I ask myself firmly, and the answer is always clear.

Please, beloved sister, take care. Do not inflame the Germans further, even if they are your captors. Do not take risks, no matter how great the impulse. All that matters is that you return to us safely; you and Jean-Michel and your beloved Édouard. I tell myself that this letter will reach you. I tell myself that perhaps, just perhaps, the two of you are together, and not in the way that I fear most. I tell myself God must be just, however He chooses to toy with our futures this dark day.

Stay safe, Sophie.

Your loving sister

Hélène

21

Paul puts down the letter, obtained from a cache of correspondence stockpiled by resistance operatives during the First World War. It is the only piece of evidence he has found of Sophie Lefèvre’s family and it, like the others, appears not to have reached her.

The Girl You Left Behind is now Paul’s priority case. He ploughs through his usual sources: museums, archivists, auction houses, experts in international art cases. Off the record, he speaks to less benign sources: old acquaintances at Scotland Yard, contacts from the world of art crime, a Romanian known for recording almost mathematically the underground movement of a whole swathe of stolen European art.

He discovers these facts: that Édouard Lefèvre had, until recently, been the least famous artist of the Académie Matisse. There are only two academics who specialize in his work, and neither of them knows any more than he does about The Girl You Left Behind.

A photograph and some written journals obtained by the Lefèvre family have turned up the fact that the painting hung in full view in the hotel known as Le Coq Rouge in St Péronne, a town occupied by Germans during the First World War. It disappeared without trace some time after Sophie Lefèvre was arrested.

And then there is a gap of some thirty years before the painting reappears, in the possession of one Louanne Baker, who kept it in her home in the US for thirty years until she moved to Spain, where she died, and David Halston bought it.

What happened to it between those dates? If it really was looted, where was it taken? What happened to Sophie Lefèvre, who seems to have simply vanished from history? The facts exist, like the dots in a join-the-dots puzzle but one in which the picture never becomes clear. There is more written about Sophie Lefèvre’s painting than there is about her.

During the Second World War, looted treasures were kept in secure vaults in Germany, underground, protected. These artworks, millions of them, had been targeted with military efficiency, aided by unscrupulous dealers and experts. This was not the random plunder of soldiers in battle: this looting was systematic, controlled, regulated and documented.

But there is little surviving documentation from the First World War, regarding looted property, especially in northern France. It means, Janey says, that this is something of a test case. She says it with some pride. For the truth is, this case is vital to their company. There are increasing numbers of organizations like theirs springing up, all sourcing provenance, listing works that relatives of the dead have spent decades trying to trace. Now there are no-win no-fee firms undercutting them, promising the earth to people who are willing to believe anything to get their beloved object back.

Sean reports that Liv’s lawyer has tried various legal means to get the case struck out. He claims that it falls beyond the statute of limitations, that the sale to David from Marianne Baker had been ‘innocent’. For a variety of complicated reasons, these have all failed. They are, says Sean, cheerfully, headed to court. ‘Looks like next week. We have Justice Berger. He’s only ever found for the claimant in these cases. Looking good!’

‘Great,’ says Paul.

There is an A4 photocopy of The Girl You Left Behind pinned up in his office, among other paintings missing or subject to restitution requests. Paul looks up periodically and wishes that every time he did so Liv Halston wasn’t looking back at him. Paul switches his attention to the papers in front of him. ‘This image is such as one would not expect to find in a humble provincial hotel,’ the Kommandant writes to his wife at one point. ‘In truth I cannot take my eyes from it.’

It? Paul wonders. Or her?

Several miles away, Liv is also working. She rises at seven, pulls on her running shoes and heads off, sprinting alongside the river, music in her ears, her heartbeat thumping along with her footsteps. She gets home after Mo leaves for work, showers, makes herself breakfast, drops a tea in with Fran, but now she leaves the Glass House, spending her days in specialist art libraries, in the fuggy archives of galleries, on the Internet, chasing leads. She is in daily contact with Henry, popping in whenever he asks to hold a conference, explaining the importance of French legal testimony, the difficulty of finding expert witnesses. ‘So basically,’ she says, ‘you want me to come up with concrete evidence on a painting about which nothing has been recorded of a woman who doesn’t seem to exist.’