Della was very happy with her flat. It was utterly quiet, a little sanctum tucked at the back of the house. She never heard a sound from her neighbours in the other parts of the house and they, of course, never heard a sound from her. She encountered them occasionally when crossing from her own front door to the front door of the house. They were mouselike people who scuttled off to their holes with no more than a nod and a ‘good evening.’ This was as it should be. The flat, too, was entirely as it should be.

The bed-sitter looked just like a living-room by day, for the bed was let down from a curtained recess in the wall only at night. Its window overlooked the yard which Della never used. She never unbolted the side gate or the back door or, needless to say, attempted to undo the screws and open the window more than six inches.

Every evening, when she had washed the dishes and wiped down every surface in the immaculate well-fitted kitchen, had her bath, made her bedtime drink, and let the bed down from the wall, she went on her security rounds just as her father did at home. First she unlocked and unbolted the back door and crossed the yard to check that the side gate was securely fastened. It always was as no one ever touched it, but Della liked to make absolutely sure, and sometimes went back several times in case her eyes had deceived her. Then she bolted and locked the back door, the garden door and the bathroom door. All these doors opened out of a small room, about ten feet square – Mrs Swanson called it the garden room – which in its turn could be locked off by yet another door from the kitchen. Della locked it. She rather regretted she couldn’t lock the door that led from the kitchen into the bed-sitting room but, owing to some oversight on Mrs Swanson’s part, there was no lock on it. However, her own front door in the bed-sitter itself was locked, of course, on the Yale. Finally, before getting into bed, she bolted the front door.

Then she was safe. Though she sometimes got up once or twice more to make assurance trebly sure, she generally settled down at this point into blissful sleep, certain that even the most accomplished of burglars couldn’t break in.

There was only one drawback – the rent.

‘That flat,’ said Mrs Swanson, ‘is really intended for two people. A married couple had it before you, and before that two ladies shared it.’

‘I couldn’t share my bed,’ said Della with a shudder, ‘or, come to that, my room.’

‘If you found a nice friend to share I wouldn’t object to putting up a single bed in the garden room. Then your friend could come and go by the side gate, provided you were prepared to promise me it would always be bolted at night.’