But Grace, in her disconcerting way, stops acting like a normal person and abruptly gets back to business.

‘OK. Rule number one. Keep an eye on your tour group at all times. We’ve had a lot of trouble with people trying to steal souvenirs. It’s always the most unlikely people too. Once, Veronika insisted this old lady empty her handbag and she’d taken two lace doilies. She said they reminded her of her childhood home.’

‘Oh, poor thing,’ says Sophie.

‘Rule number two. You probably know this from when you’ve done the tour yourself. Nobody except you goes into the corded-off rooms. They have to stand in the doorway while you point things out. Some of them will beg you to let them in. I remember one man even offered Thomas a bribe.’

‘He told me about that. He was horrified, of course.’

‘Yes, he’s always been a good boy. If it was Grandma Enigma taking the tour, she’d probably have negotiated for more.’

Grace unhooks the red cord from the doorway of the kitchen and gestures for Sophie to go ahead of her.

‘Now, for a proper Aunt Connie–authorised tour, you should really come in early and light the fuel stove, and then just before the tour starts you put the kettle on.’ She gestures at the large copper kettle sitting on top of the squat fuel stove. ‘That way, as you’re leading the group down the hallway the kettle can actually be whistling while you’re saying, “As sisters Connie and Rose walked down the hallway they could hear the sound of the kettle boiling and smell a freshly baked cake. Nothing seemed amiss.” But, to be honest, I think Margie is the only one who still bothers with actually boiling the kettle these days. The one thing you do have to remember is to cook the marble cake. The brochure says it’s made to the original recipe but I’m afraid that’s slightly misleading. Well, completely misleading. We all have our own versions. I’ll give you my recipe.’

‘Oh, I’m sure I could find a good packet mix for marble cake,’ says Sophie.

Grace laughs politely as if she’s making a joke, and Sophie thinks, Oh dear. She tiptoes reverently across the brown lino floor of the kitchen. ‘It gives me goose-bumps with just us being in here.’

‘Probably because it’s freezing.’ Grace bounces up and down on the balls of her feet, her hands tucked into her armpits. ‘So, when you’re describing the kitchen you leave the chair and the bloodstains until last. Explain how Alice had to cope without running water or electricity or food processors or microwaves. No fridge. They didn’t even have an icebox. There’s something called a Drip Safe out on the veranda. If you’ve got any women over seventy in your group, expect lots of interruptions. They’ll want to tell you about how their lives during the Depression were even harder than Alice’s. It’s a mistake to look in the slightest bit interested. They’ll never shut up. Aunt Connie used to say, “You must tell me about that after the tour.” By the way, make sure you don’t touch anything while you’re walking around the kitchen. People take the “nothing has been touched” line very seriously.’

‘Nothing has been touched, has it?’ asks Sophie, who is one of those people.

‘Margie does the dusting and she’s very careful. But Enigma is picking up things all the time, and once Veronika was doing the tour and she tripped over the upturned chair and knocked the crossword and pen flying. So, I’d say the crime scene has been pretty well contaminated.’

Sophie looks closely at the crossword sitting on the scrubbed kitchen table. The page from the newspaper is folded into a square and a Bic pen is sitting on the paper. Whoever was doing the crossword was halfway through writing out the word ‘brilliant’ in 3 across.

‘I wonder if it was Alice or Jack doing the crossword.’

‘Jack, I would think, while poor Alice was slaving away baking the cake.’

‘It looks like a woman’s handwriting to me.’

‘Does it?’ Grace makes a non-committal sound and continues on with her instructions. ‘So, once you’ve painted a picture of domestic bliss, you point out the chair and the blood stains. Somebody will ask how you can be sure they’re blood stains. Just give them a frosty look and say, “We can’t be sure. We can’t be sure about anything in this house except that it’s a mystery.”’

Sophie crouches down to examine the trail of brownish stains leading from the back door to the chair. ‘It doesn’t look like enough blood for somebody to die.’

‘I’m quite sure Aunt Connie didn’t kill anybody,’ says Grace. ‘Veronika just can’t forgive her for leaving her house to you. Shall we do the bedroom next?’

The bedroom is tiny, almost filled by a double bed with a pale pink eiderdown. Next to the bed is a wash stand with a basin and jug, and, of course, the crib.

‘Make sure you point out the indentation in the pillow where the baby’s head was,’ says Grace. ‘They love that.’

Sophie peers in the crib. ‘Actually, I can’t see it.’

Grace puts her hand in the crib and smooths out a hollow in the shape of a baby’s head. ‘There you go.’

Sophie shakes her head and laughs. ‘You’re starting to spoil the magic.’

‘Aunt Margie washes the linen every month.’

‘Oh.’ Sophie pauses. ‘I wonder how your Grandma Enigma feels when she sees this crib,’ she says to Grace. ‘Her parents obviously cared for her and she never knew them, or even knew what happened to them.’

‘Oh, sometimes she pretends to get all sentimental about it, but really she loves being the Alice and Jack baby. Wait till you see her swanning around at the Anniversary next month.’

‘Maybe, deep, deep down in her subconscious she’s still yearning for her real mother,’ says Sophie. ‘They say babies can recognise their mother’s voice by the time they’re born.’

‘Babies don’t care who looks after them, as long as they’re fed. And clean.’

‘You don’t think Jake would miss you if you disappeared?’

‘He wouldn’t miss me in the slightest.’

‘Oh, of course he would!’

‘He wouldn’t. He’d grow up and he wouldn’t remember a thing about me.’

‘Well, maybe not consciously.’