St Cordula’s Catholic boarding school has survived for centuries on tradition, discipline and silence.

Now its future is under threat, and Deputy Head Fiona Fox is preparing to lead the controversial change that could save it from ruin. But St Cordula’s has always had rules of its own. Legend has it that the ghost of fifteenth-century nun, Sister Matilda, will keep the school safe.

But only as long as the words ‘GOD FORGIVE ME’, scrawled by Matilda on a chapel staircase wall before she fell to her death, remain. Every year, the words are repainted. The only time they were allowed to fade, in 2002, a terrifying outbreak of vertigo swept through the pupils.

One girl died on the night stairs. And only three people know what really happened. Now the vertigo is back, and as panic sweeps the school, Fiona must confront a dark secret from her past. Or face the deadly consequences.