Mary is halfway downstairs when she sees the swoop of headlights arcing away from the house through the frosted glass of the front door. She picks up her pace. Pulls a jacket from the peg by the door, keys already strategically placed in the pocket. She’s been doing this for two weeks now, ever since she decided that ignorance was no longer bliss. The coat slides over the silk robe with a whisper and she’s in her Mini Cooper, engine running, before the twin ruby pinpricks of brake lights have turned the far corner. She keeps her headlights off until he’s out of sight, then starts to mentally rehearse the excuse she has prepared in case she’s rumbled. Splitting headache. No paracetamol in the house. Keep it simple.

She’s relieved to see there’s still enough traffic on the road that she doesn’t stand out too easily. Mainly taxis, but at this time of night all Alexander will see in his rear-view are headlights either way. She mutters to herself as she drives. Tells herself again what a bad idea this is, but curiosity drives her on. She reminds herself it also killed the cat, but carries on undeterred. Mary sees him make a turn. At least she thinks it’s him. She reaches the junction, sees that she was right, and panics because there’s nobody else on the road now. Just him and her. She eases up on the accelerator, staying far enough back that she gets palpitations every time his lights disappear around a corner, not letting up until she rounds the bend.

She frowns as she sees the sign at his latest detour. Ruislip Lido. Her father used to bring her here as a child. At least once a month, weather permitting, she and her sister would squeeze into the back seat of her dad’s pale cream Austin 7 and spend the day exploring the woods or splashing in the waters of the lido. It’s seen better days, though. Not that Alexander would be heading there for a swim at this time of night, anyway.