Lena never liked Mondays, but this one was particularly strange right from the start of the morning. As she descended the stairs from the third floor of her old block of flats, she realised that there was a different smell on each floor: vanilla, old paper and even.... ozone, like after a storm. She stopped in the stairwell, pulling out her phone, wanting to text Nina, her friend, but saw that her screen flashed a strange purple light and suddenly went out. She sighed heavily and started to walk further down. On the second floor in the doorway she passed Mr Hare, a neighbour who was usually sullen, but today he smiled mysteriously at her and winked. "Today everything is going to go the other way, Lena," he said, and his voice sounded as if it came from behind a thick curtain. The lower she descended, the more unusual the world became. The tiles of the staircase seemed to pulsate slightly underfoot, and the light of the bulbs flicked to the rhythm of her steps. Reaching the first floor, Lena noticed that the door leading to the basement was ajar. Strange, silvery streaks of light seeped through the gap, rippling as if trying to attract her. She knew she should go to school, but curiosity was stronger. She scowled, glanced over her shoulder at the empty staircase and gently pushed open the basement door. She heard a quiet whisper, as if someone had called her name. She felt that from this moment on, nothing would be the same as before, and that the stairwell was no longer just a daily route to lessons. With a trembling heart, she went down a few steps and then, behind her back, the door slammed with a bang and the whole corridor glowed with an unusual light....