Nicci French is the pseudonym for the writing partnership of journalists Nicci Gerrard and Sean French. The couple are married and live in Suffolk. There are twelve other bestselling novels by Nicci French: The Memory Game, The Safe House, Killing Me Softly, Beneath the Skin, The Red Room, Land of the Living, Secret Smile, Catch Me When I Fall, Losing You, Until It’s Over, What To Do When Someone Dies and Complicit, all published by Penguin. Blue Monday is the first thrilling instalment in the Frieda Klein series.

To Edgar, Anna, Hadley and Molly

In this city there were many ghosts. She had to take care. She avoided the cracks between the paving stones, skipping and jumping, her feet in their scuffed lace-up shoes landing in the blank spaces. She was nimble at this hopscotch by now. She had done it every day on the way to school and back ever since she could remember, first holding on to her mother’s hand, dragging and jerking her as she leaped from one safe place to the next; then on her own. Don’t step on the cracks. Or what? She was probably too old for such a game now, already nine, and in a few weeks’ time she would be ten, just before the summer holidays began. Still she played it, mostly out of habit but also nervous about what might happen if she stopped.

This bit was tricky – the paving was broken up into a jagged mosaic. She got across it, one toe pressing into the little island between the lines. Her plaits swung against her hot cheek, her school bag bumped against her hip, heavy with books and her half-eaten packed lunch. Behind her, she could hear Joanna’s feet following in her steps. She didn’t turn. Her little sister was always trailing after her, always getting in her way. Now she heard her whimpering: ‘Rosie! Rosie, wait for me!’