One summer evening, the girls were all sitting around the dining-room table, a sultry breeze blowing in from the open door to the garden. Carmen was bustling around the kitchen. She was a creature of habit and had little rituals that she followed regularly. Every evening, she would send the girls up to bed and follow a little while later with a tray of hot drinks and biscuits. But tonight, it was not to be. She suddenly went deathly pale and stifled a scream. “Fiona, shut the antiporta,” she yelled and then, to the girls’ bewilderment, she turned and ran out of the room, up the stairs. They heard the room of her bedroom slam shut and the key turn in the lock. And then there was silence. They had no idea what was wrong. They tried to work out what could have happened but the only thing that Fiona remembered was the sound of the light switch flicking on and off. Not that that would have meant anything. It was one of the days when they did not have any electricity and the room was lit by a large oil lamp. And she also heard the door handle rattle slightly after her mother left the room but it did not open and she thought it was just the way her mother had slammed it. The girls...