The shadow exhaled deeply, emerged from the shadows and quietly climbed the stairs.

To watch.

To wait.

To exact long-awaited retribution.

2

FOUR DAYS LATER

The night air was close and humid on the quiet South London street. Moths fizzed and bumped in the orange arc of light cast by a streetlamp illuminating a row of terraced houses. Estelle Munro shuffled along the pavement, arthritis slowing her progress. When she drew close to the light, she stepped down from the pavement and onto the road. The effort to step down off the kerb made her groan, but her fear of moths outweighed the pain in her arthritic knees.

Estelle eased her way through a gap between two parked cars and gave the streetlight a wide berth, feeling the heat from the day’s sun radiating off the tarmac. The heatwave was in its second week, pressing down on the residents of London and the south-east of England, and along with thousands of other old people Estelle’s heart was protesting. The siren of a far-off ambulance blared, seeming to echo her thoughts. She was relieved to see that the next two streetlights were broken, and slowly, painfully, she edged between two parked cars and rejoined the pavement.

She had offered to feed her son Gregory’s cat whilst he was away. She didn’t like cats. She’d only offered so she could have a good nose around the house, and see how her son was coping since his wife, Penny, had left him, taking Estelle’s five-year-old grandson, Peter, with her.

Estelle was out of breath and pouring with sweat when she reached the gate of Gregory’s smart terraced house. In her opinion, it was the smartest house in the whole street. She pulled a large hanky out from under her bra strap and wiped the sweat off her face.

Light from the orange streetlight rippled across the glass front door as Estelle fished out her key. When she opened the door, she was hit by a wall of stifling heat and she stepped reluctantly inside, onto letters strewn over the mat. She flicked the light switch by the door, but the hallway remained in darkness.

‘Bloody hell, not again,’ she muttered, pulling the door closed behind her. As she felt around to pick up the post, she realised this was the third time the power had tripped whilst Gregory had been away. The lights in the fish tank had done it once before, and another time Penny had left the bathroom light on and the bulb had blown.

Estelle fished her mobile phone from her handbag and, with an awkward fumble of gnarled fingers, unlocked the screen. It cast a dim halo of light a few feet in front, illuminating the pale carpet and narrow walls, and she jumped as she saw her ghostly reflection in the large mirror on the left-hand side. The half-light gave the lilies on her sleeveless blouse an inky, poisonous quality. She focused the light of her phone down onto the carpet and shuffled towards the living room door, feeling around on the inside wall for the switch, to check it wasn’t just the hall bulb that had gone. She flicked the switch on and off, but nothing happened.

Then the screen of her phone timed out and she was plunged into total darkness. Just the sound of her laboured breathing filled the silence. She panicked, fumbling to unlock the phone. At first her arthritic fingers wouldn’t move fast enough, but finally she managed it and the light came back on, casting the front room in a circle of dim blue.

It was stifling inside: the heat pressed down on her, closing off her ears. It was as if she were underwater. Dust particles twirled in the air; a cloud of tiny flies floated silently above a large arty china plate filled with brown wooden balls on the coffee table.

‘It’s just a power cut!’ she snapped, her voice resonating sharply off the iron fireplace. She was annoyed that she’d panicked. It was just the circuit breaker, nothing more. To prove there was nothing to be scared of, she would first have a drink of cold water, and then she would get the electricity back on. She turned, shuffling purposefully off towards the kitchen, her arm outstretched with the phone.

The glass kitchen seemed cavernous in the phone’s half-light, extending out into the garden. Estelle felt vulnerable and exposed. There was a distant whoosh and a click-clack as a train passed on the track beyond the bottom of the garden. Estelle went to a cupboard and pulled down a glass tumbler. Sweat stung, as it dripped into her eyes; she wiped her face with her bare arm. She moved to the sink and filled her glass, wincing as she drank the lukewarm water.

The light went out on the phone again, and a crash from upstairs broke the silence. Estelle dropped the tumbler. It shattered, glass spraying out on the wood floor. Her heart pulsed and pounded, and as she listened in the darkness there was another scuffling sound from above. She grabbed a rolling pin from a pot of utensils on the counter and went to the bottom of the stairs.