‘What happens if you do?’

Helga remembers that night swim when she and Linus had got into trouble. It had been summertime, but the Scandinavian nights are always cold. It was their first holiday together. She’d taken him home to introduce him to her grandmother and, with her blessing, they’d taken her beloved old camper van to the coast.

‘In cold water, they reckon that anywhere between five and thirty minutes, you cool down too much for your fingers and forearms to move.’

She pictures Linus, his blond hair falling in his face, his lips blue in the moonlight as he fumbled with the keys to the van, unable to turn them in the lock and dropping them in the sand, the tide coming precariously close.

‘It’s scary. It happened to me once. I lost all coordination and was stumbling around like a drunk woman.’ She remembers staggering to the van and how they’d moved to safety just in the nick of time, the tyres crunching over the carpet of pine needles as they’d retreated through the trees from the water’s edge. How they’d stripped off and clung to each other naked under the blankets on the mattress, their lips blue, their teeth chattering. How they’d both been scared and how she’d never wanted to let him go. Why does she remember all these things so clearly, when some of the intervening decades are fuzzy and lost?

‘That’s it. Splash your forearms and the back of your neck.’

Dominica swims over, a few languid strokes of front crawl.

‘You’ve put your face under,’ Maddy says, clearly impressed.

‘That’s to stimulate the vagus nerve.’

‘The vagus nerve? Sounds like something to do with gambling.’

‘It’s one of the biggest nerves in the body,’ Helga explains. ‘It runs all down here’ – she puts her hand up to her face and throat – ‘and right down to the abdomen. In fact, it goes everywhere. Vagus means wanderer in Latin, so it wanders all over the place to all your organs. Basically, when you get into cold water your fight or flight nervous system kicks in. But here’s the thing. Cold water also stimulates the vagus nerve, which does the opposite. It kicks in your parasympathetic nervous system.’

‘Did you know that pharmaceutical companies try and mimic the vagus nerve when they make antidepressants?’ Dominica adds, as an aside.

Helga gives her a frown. They’ve spoken about the pills the doctor prescribed to Dominica, and Helga made it clear that, in her view, it’s a mistake to start pills, when her grief is unavoidable. It’s a process. Just like everything else in life. Taking pills for it doesn’t stop that process, just dulls it. And what’s the point of life being dull? As far as Helga’s concerned, emotions are like internal weather and she’s a great believer in experiencing all extremes of weather. After all, you can’t go through life expecting nothing but sunny days. That’s not realistic. You have to have the grey, boring days, or the relentlessly rainy ones to appreciate the sun when it comes out.