Being so close to law enforcement officers made Friday’s heart race. Most of the officers were involved in searching the cars coming the other way. There was just one officer on their side of the checkpoint, sitting on a stool. He wasn’t even watching them. He was looking south, watching a pedestrian coming from the Swiss side. The pedestrian looked like a student. He wasn’t carrying anything. He was about as unthreatening as a cross-border pedestrian could be. The guard didn’t look like he was going to bother getting up from his seat. This was evidently a low-energy operation.

  Friday tried to act naturally as she walked towards the checkpoint. But she suddenly forgot how. Her legs felt like jelly. She didn’t know what to do with her hands. Should she swing them back and forth? Should she hold them dead straight? What did she do with her hands when she was walking? She couldn’t remember.

  Friday glanced across at the checkpoint again. They’d finished searching the car and it pulled away. The line of traffic edged forward and a van pulled up. The customs officers were still ignoring her and Melanie. Friday increased her speed. She wanted to get safely into Switzerland. There was literally a line marking the border painted on the sidewalk. Friday stepped forward, about to put her foot on Swiss soil, when suddenly she was startled by the guards yelling . . .

  ‘Trauben! Trauben!’

  Friday flinched and stumbled. She looked across to see two of the officers grab the van driver and put him in handcuffs.

  ‘What’s happening?’ asked Melanie.

  ‘Trauben means grapes,’ said Friday. ‘They must have found grapes in the van.’

  They both glanced back to get a glimpse of the van as they kept walking, when suddenly – SLAM! Friday walked straight into the student coming the other way.

  ‘Sorry,’ said Friday.

  Something fell out of the student’s jacket and hit the ground. It was a plastic tube. The type of cylinder you might use to send documents through the mail. It hit the ground and rolled into the street. The customs officer on the stool turned around to see what the sound was. The student lunged forward to grab the tube. The customs officer snapped into action. He launched himself off his stool at the student, knocking the tube out of his reach. The tube rolled over to Friday, stopping at her feet. Friday started to bend down to pick it up.

  ‘Don’t,’ said Melanie, grabbing her hand. ‘This is our distraction. We need to use it.’

  ‘But . . .’ said Friday.

  ‘We’re sneaking across an international border,’ said Melanie. ‘Now is not the time.’

  They hurried way. Friday could still hear the scuffle taking place behind them.

  ‘What do you think was in the tube?’ asked Melanie.

  ‘I don’t know,’ said Friday. ‘An artwork? A blueprint? A stick of plutonium? But it must be something important to set up that decoy.’

  ‘What decoy?’ asked Melanie.

  ‘The van full of grapes,’ said Friday. ‘It was so obvious. Anyone really trying to smuggle grapes out of Switzerland would hide them in a bigger van, behind something else, so the border guards would miss it. They wanted to be stopped and arrested, to distract the guards from the student with the tube.’

  ‘Well, they got him,’ said Melanie.

  ‘Yes,’ said Friday, glancing back over her shoulder. ‘Unless it was a double decoy for something else.’

  ‘It was,’ said Melanie. ‘It was a double decoy for us. Thanks to that fuss, we’re in Switzerland.’

  Friday realised they were now 50 metres into Swiss territory, and no-one had stopped them. ‘We made it,’ she said. ‘We’re in.’

  ‘Yes, I know. It was very anti-climactic in the end,’ said Melanie. ‘After the chase in Paris and the disguises, I was expecting something more dramatic – like a scene from a movie with us running across no-man’s land between the two countries in a hail of gun-fire.’

  ‘Really?’ asked Friday.

  ‘No,’ admitted Melanie. ‘But I was at least expecting a person to glance at us.’

  ‘Maybe they’ve caught Ian,’ said Friday. ‘And they all get to go home for the day when they’ve caught one suspected terrorist.’

  ‘You’re such a Nelly Negative,’ said Melanie. ‘Ian probably just met a sweet old granny on the train who offered to drive him to CERN to save him travelling on a bus.’

  Friday wanted to believe Melanie. Ian did always charm his way out of any scrape. But she preferred it when she was with him while he did it.

  Once they were across the border, it did not take Friday and Melanie long to get to CERN. They only had to walk another 400 metres down the road and the visitors welcome centre was on the left. It was impossible to miss because the building was a large rusty-orange coloured dome.

  ‘It looks like an observatory,’ said Melanie.

  ‘Which is ironic,’ said Friday. ‘Observatories use powerful telescopes to look out into the infinite, undiscovered realm of space. Whereas CERN looks into the unimaginably tiny realm of subatomic particles.’

  ‘So what does the dome do?’ asked Melanie.

  ‘Nothing,’ said Friday. ‘It’s just a tourist attraction. Something to take a selfie in front of. The actual super collider is underground.’

  ‘Where do we start?’ asked Melanie. ‘Do we search for evidence to exonerate your mother? Or are we going to interview people? Do we need to change our disguises so we look like visiting scientists?’

  ‘We haven’t got time to faff about,’ said Friday. ‘Let’s just go and say hello.’

  She started striding up the path to the main entrance.

  The lobby was huge and the design minimalist. The floor was polished concrete, shining an almost obsidian black. The ceiling arched high like a cathedral. There were no pictures on the walls or objects on display. There was just one thing hanging on the wall directly in front as they came in through the front doors – a blackboard. It was an old-fashioned blackboard with a timber frame. The type you would have found in any classroom in the 20th century. In fact, this blackboard was so old it wasn’t really black, it had more of a greenish hue. And an equation was written on it in yellow chalk.

  ‘Wow!’ said Friday in awed wonder.

  ‘What is that?’ asked Melanie.

  ‘That’s where it all began,’ said Friday, walking towards it for a closer look. ‘That equation describes the Standard Model of physics. Everything that physicists understand about the fundamental building blocks of the universe can be boiled down to that.’

  ‘Okay,’ said Melanie.

  ‘It’s beautiful,’ said Friday. Her face glowed with admiration for the object in front of her.

  ‘It’s a blackboard,’ said Melanie.

  ‘It was taken from the classroom of Professor Peter Higgs at Cambridge University,’ said Friday. ‘His work inspired the construction of this facility. The Higgs boson particle was named after him when it was discovered here at CERN. That’s his handwriting.’

  ‘Oh, look,’ said Melanie. She had noticed a gift shop at the far end of the lobby. ‘You can get it on coffee mugs as well.’

  Friday turned. The gift shop was full of CERN souvenirs featuring the CERN logo, but there were also lots of tea towels, postcards, coffee cups and t-shirts featuring the Standard Model Lagrangian as it was written on the blackboard.

  ‘That is so cool,’ said Friday. Her instinct was to go over and buy a t-shirt, but she did have her mother to find, so she glanced about looking for a reception desk.

  There was a long counter where tourists were lining up to buy tickets for the museum and tours of the facility. But on the other side of the room, there was a more modest reception desk. It looked more like a reception desk in a dentist’s office. This was the gateway to the real facility, the part the public didn’t get to see, which was most of it.

  Friday walked over and stood at the counter. The receptionist did not look up. She must have heard them coming – their shoes squeaked on the concrete floor.

  Friday was full of adrenaline from evading the Paris police, illegally crossing the border and losing her boyfriend. She didn’t have the patience to wait. ‘Hello,’ she prompted.

  The receptionist glanced up, holding up a finger to indicate that she wanted Friday to wait while she did something on her computer. Friday waited patiently for 30 seconds while the receptionist hit several keys, then sighed and gave them her full attention.

  ‘Sorry, that was an online auction,’ said the receptionist. ‘I was trying to get a mint condition Asterix and Obelix doona cover, but I was outbid in the last two seconds by someone in Japan.’

  ‘I’m sorry for your loss,’ said Friday.

  ‘Friday, did you just do sarcasm?’ asked Melanie.

  ‘No,’ said Friday. ‘I was trying to do lying. I don’t care about her doona cover. I think it’s inappropriate to do online shopping in the workplace, but I want her to help me, so I thought it would be better to fake sympathy.’

  ‘Well done,’ said Melanie. ‘I’m so pleased you’ve finally started using deductive reasoning on working out how to do appropriate emotional response.’

  ‘Did you want something?’ asked the receptionist. ‘Or can I get on with what I was doing?’

  ‘What are you shopping for next?’ asked Melanie.

  ‘There’s a Snoopy clock up for auction in half an hour,’ said the receptionist.

  ‘Nice,’ said Melanie.

  ‘We’re here to see Dr Halley Barnes,’ said Friday.

  ‘Do you have an appointment?’ asked the receptionist.

  ‘No,’ said Friday.

  ‘The PAN team doesn’t like unscheduled interruptions,’ said the receptionist.

  ‘It’s a family emergency,’ said Friday.

  ‘That’s what they all say,’ said the receptionist. ‘Are you a collider groupie? Did you get the name of one of our scientists so you can try to sneak inside and get a look at the experiment?’

  ‘No, I just want to talk my sister,’ said Friday.

  ‘Your sister?’ said the receptionist, suddenly impressed. ‘So you’re Dr Quasar Barnes?! The Dr Quasar Barnes!’

  ‘No, that’s my other sister. She doesn’t work here. She’s at Zurich University along with my father, Dr Harold Barnes, and my oldest brother, Dr Orion Barnes,’ said Friday. ‘I’m the youngest one in the family. Friday Barnes.’

  ‘She’s not a doctor,’ said Melanie. ‘She got thrown out of university.’

  ‘I’ll see if Dr Halley Barnes will take your call,’ said the receptionist. She dialled a number. It rang for a long time before someone picked up.

  ‘Hello, sorry to interrupt, Dr Barnes,’ said the receptionist. ‘There’s someone here to see you in reception. She claims to be your sister. She says her name is Friday.’

  The receptionist glanced up at Friday.

  ‘About fifteen, spikey blonde hair, and a nose ring,’ said the receptionist. ‘Uh-huh, no. No brown cardigan. Uh-huh, I’m sorry, so sorry.’

  The receptionist hung up.

  ‘She says you’re not her sister,’ said the receptionist. ‘She says her sister is a thirteen-year-old brunette.’

  ‘But I am her sister,’ said Friday. ‘She just hasn’t seen me for four years. She’s got my age wrong, and she doesn’t know what I look like.’

  ‘I can’t call her back,’ shrugged the receptionist. ‘She said her research is at a crucial stage and she was pulling the phone out of the wall.’

  ‘Typical,’ said Friday. ‘Fine. Is my brother here? Dr Quantum Barnes?’

  ‘Never heard of him,’ said the receptionist.

  ‘He does exist,’ said Friday. ‘He’s a theoretical physicist connected to the MoEDAL-MAPP experiment.’

  ‘If you say so,’ said the receptionist. She consulted her computer. ‘Oh, you’re right. But he doesn’t have a phone.’

  ‘Why not?’ asked Friday.

  ‘A lot of the theoretical physicists don’t,’ said the receptionist. ‘They don’t like the distraction. He’s in J building.’

  ‘Okay,’ said Friday. ‘Thank you.’

  ‘Whatever,’ said the receptionist.

  Friday and Melanie turned to leave.

  ‘Hey!’ said the receptionist. ‘This isn’t you, is it?’ She tugged a piece of A4 paper from her side of the reception desk. She looked at it closely, then looked up at Friday. She turned the page to show them. It was a security warning, with a blown-up photograph. It was Friday’s mugshot from when she had been detained by police two years earlier. The printout was grainy, her outfit was totally different and her hair was a different shade, but it was clearly her. The receptionist reached this conclusion at the same moment as Friday.

  ‘Run!’ cried Friday.

  She turned, grabbed Melanie and sprinted for the door. Before they burst out, they could hear the receptionist yelling into her phone. ‘I need to report a terrorist!’

  ‘Where to?’ asked Melanie.

  Friday glanced about. She spotted a building with a large ‘H’ on it.

  ‘That way,’ said Friday. ‘J must be nearby.’

  They took off sprinting.

  ‘Do we have to run this fast?’ panted Melanie. ‘Surely the police won’t arrive here instantaneously.’

  ‘No,’ said Friday. ‘But I’d like to have a couple of minutes to talk to Quantum before I’m shoved in a paddy wagon.’

  ‘There!’ said Melanie. As they passed building I they saw J around the corner. It was a single-storey demountable. From the configuration of the windows, it looked like there was a series of small offices inside.

  ‘Come on,’ said Friday. ‘We don’t want to talk to another receptionist. If we look through the windows we should find him.’

  ‘Unless he’s in the toilet,’ said Melanie.

  ‘What is it with you and toilets?’ asked Friday.

  ‘It’s always a possibility,’ said Melanie.

  There were eight offices on the first side of the building. Five of them were empty. The other three had scholars who were clearly not her brother. They were either too old, too female or both. But when they turned the first corner Friday soon spotted him through the second window. He was hunched over his desk writing on a notepad. He was distinctive looking. Like all of Friday’s siblings, Quantum was tall and incredibly good-looking. He had golden-brown hair, a lanky physique and a permanently irritated manner, all of which combined gave him the look of a runway model bored with his own glamour.

  The office was very small, only about three metres by three metres, but inside that small space it looked like a bomb had gone off. There were notepads, periodicals and pens littered everywhere. In the middle of it all, Friday’s brother sat completely still, totally absorbed in his calculations. Oblivious to the mess.

  Friday banged on the glass of the window. ‘Quantum!’ she cried.

  Her brother didn’t notice.

  ‘Is he deaf?’ asked Melanie.

  ‘Only selectively,’ said Friday. She banged on the window again. ‘Quantum!’

  He still didn’t respond.

  ‘Do you think the window is double-glazed?’ asked Melanie.

  ‘No, I think his brain is double-glazed,’ said Friday. ‘I haven’t got time for this.’ She looked about and noticed a brick propped under a downpipe nearby. She yanked it out, causing the downpipe to sag out from the guttering above. But Friday wasn’t concerned about plumbing. She was striding back to her brother’s window.

  ‘Cover your eyes,’ she advised Melanie, before throwing the brick at the window. Friday was not an athletic person, and bricks are surprisingly heavy, so she wasn’t able to throw it with as much force as she would have liked. The brick hit the window, which splintered into a cobweb of cracks, bounced off and thudded to the ground.

  It did have the effect of catching Quantum’s attention, though. He stood up, walked over to the vandalised window and slid it open.

  ‘Friday?’ said Quantum. ‘Is that you? Have you done something different to your hair?’

  ‘Well done noticing,’ said Melanie. ‘Friday looks lovely, doesn’t she?’

  ‘Not my area of expertise,’ said Quantum. ‘Was my window always like that?’ he asked, looking at the cracked glass.

  ‘We’re here to help Mum,’ said Friday. ‘What happened? What was she arrested for?’

  ‘Mum?’ said Quantum.

  ‘Our mother,’ said Friday. ‘The woman who birthed us.’

  ‘Oh, Dr Barnes,’ said Quantum.

  ‘Do all your family refer to each other by their academic titles?’ asked Melanie.

  ‘Yes,’ said Friday. ‘And, no, it doesn’t get less confusing when you get used to it.’

  ‘Why are you bothering me?’ asked Quantum.

  ‘We need to know what happened,’ said Friday. ‘Why was Mum arrested?’

  ‘But I don’t know anything,’ said Quantum.

  ‘That I believe,’ said Melanie.

  ‘You probably do, you just don’t know what you know,’ said Friday. ‘Talk me through what happened.’

  ‘When?’ asked Quantum.

  ‘The day she was arrested,’ said Friday. ‘What happened before she got arrested? What did she do?’

  ‘Which day was that?’ asked Quantum.

  ‘I don’t know. I wasn’t here,’ said Friday. ‘You were. You must remember the day your mother was arrested.’

  ‘No,’ said Quantum. ‘They say there was some yelling. But I didn’t notice it myself. I was working on a new algorithm that day. It took a great deal of concentration.’

  ‘Have you been allowed to see her?’ asked Friday.

  ‘See her?’ said Quantum. ‘But it’s a workday. I haven’t had time.’

  ‘Quantum, you’ve been working on the same thought experiment for four years,’ said Friday. ‘You didn’t think you could take half a day off to go down to the police station and speak to your mother?’

  ‘It didn’t occur to me that she would want me to,’ said Quantum. ‘She doesn’t like it when anyone interrupts her research.’

  ‘She’s not doing research,’ said Friday. ‘She’s locked up in a cell.’

  ‘She would like that,’ said Quantum. ‘No-one to interrupt her.’

  ‘And the toilet is right there in the room with you,’ said Melanie. ‘You don’t need to waste time on bathroom breaks.’