Tess bustles about, crooning, ‘Don’t worry, sweetheart, happens to the best of us. Give them here. We’ll leave them to soak. It’ll all come out in the wash.’ She says this last bit while looking at Lizzie, who busies herself checking for the lead and poo-bags.

Maud stays close to Lizzie on the Beacon. So close Lizzie worries she’ll trip over her. ‘Go on,’ she says, throwing a tennis ball she’d found in Maud’s basket, ‘run after it.’ But Maud just pads along silently.

‘Why aren’t you weeing on everything and rolling in dead starlings?’

Maud stops and looks at her then, head tipped to one side.

‘Not that you need to. Your ancestors did it to mask their scent. It protected them from predators, helped them sneak up on their prey. You don’t have to catch your prey. You just have to waddle to your food bowl and Pedigree Chum appears.’

Maud seems fascinated, so Lizzie carries on: ‘I’ve been looking into a better diet for you. Canagan mimics the diet your ancestors would have eaten in the wild.’

Maud barks and Lizzie says, ‘They have lots of flavours. Salmon. Chicken. Highland Feast.’ Maud barks twice at that and Lizzie says, ‘I’ll get the Highland Feast.’

She gazes at Maud in admiration. She knew about guide dogs and sniffer dogs, but she thought those dogs had all been specially bred for the jobs. She hadn’t realized any dog could be trained, potentially. Lizzie feels the fizz of an experiment bubble up inside her. Words like ‘hypothesis’ and ‘testable explanation’ whisper in her mind. Her hand opens and closes on empty air, as if she’s reaching for something already gone.

The sudden lump in Lizzie’s throat is painful. She walks to the bench, Maud half running to keep up with her. The sobs feel as if they’re choking her and her ribcage spasms. It feels like her heart is cracking, but her heart has nothing to do with it.

Maud licks her hand. It’s oddly comforting, even though Lizzie will have to wash her hands immediately after they get home. ‘There are three types of tears, Maud. Psychic, basal and reflex. Psychic tears are caused by emotions. Basal tears keep the eyes lubricated. Reflex tears are in response to something else.’

Maud carries on licking.

‘If the first tear comes from the right eye, it’s happiness. The first tear from the left means pain. They all look different underneath a microscope. Tears of joy look like a map of a city. Grief looks like boats on the sea. Onion tears look like fern leaves.’ Lizzie strokes the soft fur of Maud’s ears. They’re dappled, like they’ve been dipped in a cup of tea. ‘I don’t know which type of tears these are.’

George

(Cadbury’s and Kleenex)