Today, Valera had dressed in a dull brown blouse and the same pair of old, worn trousers she wore almost every day, and Ledjo had a small, bright red neckerchief under his white collar. This short length of fabric was the symbol of the Young Pioneers, the Soviet Union’s mass youth organisation. Technically, Ledjo was three years too young to join the Young Pioneers but Zukolev had made membership mandatory for every child in Povenets B. Young Pioneer neckerchiefs were also technically supposed to be a neatly folded triangle of plain red fabric, but Ledjo’s had recently been part of the right sleeve of one of Valera’s few brighter shirts, which she had sacrificed for her son’s happiness. From a distance it looked plain, but up close it was an abstract pattern of intermingling triangles and squares.

Young Pioneer day was Ledjo’s favourite day of the week, and he would normally be pulling on his mother’s arm to get to school as early as possible. But today he struggled to keep up with her. He kept tugging on her hand to get her to slow down, but it didn’t work.

When they reached the school gates a full twenty minutes before the fourth siren, Ledjo decided it was time for his own small rebellion against Povenets B’s draconian rules.

He let go of Valera’s hand, stepped in front of her, and said, very loudly, ‘Goodbye, Mama.’

His voice snapped Valera out of the swirling thoughts about radio waves and rake receivers that had consumed her all night. She looked down at him, really seeing him and the tears threatening the corners of his eyes properly for the first time that day.

‘Oh, Pikku, I’m so sorry.’ She opened her arms, and Ledjo rushed straight into them, his pout instantly dissolving. ‘I’ve been very bad,’ she said to the top of his head, ‘but I’ll make up for it. I think today is going to be a great day.’ She kneeled down, holding Ledjo out in front of her. ‘Be a good boy. I love you.’

‘I love you too, Mama.’

Valera smiled, turned him round, and gave him a gentle shove to start him running through the gates.

As soon as he was inside the school, she turned away, letting herself get lost in her thoughts again. She ignored the other mothers with their plaited hair and children in perfect neckerchiefs passing her on their way to school, and the men in overalls rushing to deal with the latest problem at the power plant.

Valera would never say luck had played much of a part in her life. But she had been fortunate that her natural aptitude for physics had been spotted late.