She walks purposefully through streets and squares and alleyways, never using her A–Z. When she is lost or tired, she hops onto the Tube and travels beneath the capital instead. She crosses bridges and parks and climbs high buildings, examining her world from every which way. Spiralling away from the centre, she visits markets and sits in cafes or wanders amongst stalls. From time to time she wonders if a voice she hears in the crowd might belong to her birth mother, or if a place she goes to is somewhere her mother might have been.

In Streatham, she wanders the common and sits on a bench. A tired-looking woman rocking a pram occupies the other end. Marina smiles, but the woman doesn’t notice.

Marina thinks of an article she read about a newborn, a girl, wrapped in a blanket and left in a park. She would have been warm, only there had been a storm that night. A homeless man had come across the bundle and taken her to the hospital and miraculously she had survived. Marina has read other stories too, about newborns abandoned outside churches, hospitals and houses; in fields, forests and rubbish dumps. She puts the stories into two camps: mothers wanting them to be found by priests, doctors or well-meaning people; and those who abandoned them to the elements. She thinks about motives: too young, too poor, too alone, too frightened. She imagines the secrecy of giving birth in a bath, an alleyway or a public toilet. She imagines the fear, the stifling of screams and crying in silence. She doesn’t judge.

The woman stills the pram. The baby wails. Marina tenses and glances across. There is an expression of despair on the woman’s face, but when Marina smiles this time, her face clears and she smiles back. Reaching inside the pram, she lifts out her baby to feed.

One day, Marina drives to the hospital. How strange, walking through the entrance – the buzz, the disinfectant, the slow-walking patients attached to their drips, the fast-running staff responding to calls.

She tries to imagine how it would have been nearly thirty years before. How much has changed? Different decor, uniforms, treatments and equipment. The nurses might have worn hats and capes. The doctors might all have been male. She sets the scene for the day she arrived: staff making a fuss of her, poking and prodding, checking her health, looking for clues. Interested parties: journalists and photographers. A whirl and a fuss for the baby in blue.

In the car park, she wanders, hands in her pockets. She visualises the foster parents, perhaps a social worker, Sofía and other nurses crowding round to say goodbye. She thinks about the unexplained woman. Did Ruth know that story? Had she thought it mysterious too?