Friday took a step back so he could see for himself. Someone had written all over the original equation. They hadn’t written words. They’d added to the equation, scrawling symbols around the edges and between the original lines.

  ‘That was handwritten by Dr Higgs himself in 1967,’ said the Chief Scientist. He’d followed in Dr Dalecki’s wake. ‘Who did this?’ He spun around to glare at suspects in the crowd. There were hundreds of staff members crowded in close. But his eyes settled on the person who had been closest to the crime – Friday.

  ‘You!’ he accused.

  ‘It wasn’t me,’ said Friday.

  ‘What is a child even doing here anyway?’ demanded Dr Dalecki.

  ‘This is Dr Barnes’ daughter,’ said Ms Dekker, pushing her way to the front. ‘Her youngest daughter. She has been recruited in an informal role here at CERN, to take care of her mother’s scheduling commitments.’

  ‘What?’ asked Dr Dalecki. ‘What does that even mean?’

  ‘I’m Mum’s babysitter,’ said Friday.

  ‘But your mother is a Nobel Laureate,’ said Dr Dalecki.

  ‘Yes,’ agreed Friday.

  ‘Why did you do this?’ demanded Dr Dalecki, pointing at the blackboard.

  ‘I didn’t,’ said Friday.

  ‘I saw you standing so close you practically had your nose against it,’ accused Dr Dalecki.

  ‘I was standing up close so I could observe the scene of the crime,’ said Friday. ‘When I’m not taking care of my mother, I am an investigative consultant for Interpol.’

  Melanie coughed into her hand. ‘In the arts unit.’

  ‘Well, this graffiti was done in chalk and chalk is a medium used by many artists,’ said Friday. ‘So I think this falls within my jurisdiction.’

  ‘This was an artefact of great historical importance to the scientific community, and it has been ruined,’ said Dr Ballentine. ‘If you had anything to do with it, you are in a lot of trouble, young lady.’

  ‘There is no need to use my age and gender as a pejorative,’ said Friday. ‘Besides, you’re wrong. If Dr Higgs wrote the original chalk equation in 1967, it would have been regarded as significant even in that time. There would have been efforts to preserve it. The fact that the blackboard is not framed behind glass, would confirm that assumption.’

  ‘What?’ said Dr Dalecki.

  ‘I’m pretty sure the equation is graffiti-proof. Observe,’ said Friday. She licked her forefinger, stepped forward and rubbed it on the equation.

  ‘No!’ cried Dr Ballentine.

  There were gasps and cries of shock from the crowd. Dr Dalecki grabbed Friday by the shoulders and yanked her away.

  ‘Are you some sort of activist-terrorist?’ he demanded.

  ‘No, just a detective who uses deductive reasoning,’ said Friday.

  ‘Oh, look,’ said Melanie. ‘She was right.’

  Where Friday had rubbed her saliva on the blackboard was visibly damp, but the chalk writing of the original equation had not been smudged at all.

  ‘It’s very common, particularly in Europe where street art is valued,’ explained Friday, ‘to paint over a work of art with clear graffiti-proof paint. That way if someone puts graffiti over the top, it is easily cleaned off.’

  ‘Quick,’ said Dr Dalecki. ‘Someone fetch a cloth and get the graffiti off before it dries then.’

  ‘No, you don’t want to do that either,’ said Friday.

  ‘Besides, it’s chalk,’ said Melanie. ‘That doesn’t dry. Even I know that.’

  ‘But it’s a desecration of the founding principle of this institution,’ said Dr Dalecki.

  ‘It isn’t,’ said Friday. ‘Read it.’

  Dr Dalecki looked at the equation. The standard equation was complicated to start with, but this hurriedly scrawled addition was even more confusing to take in.

  ‘What am I looking at?’ asked Dr Dalecki.

  ‘I’m not a professional theoretical physicist,’ said Friday. ‘But to me it looks like your graffiti artist has just found a way to incorporate gravity into the standard equation.’

  Now there really were gasps of shock. People started taking out their phones and taking pictures. They muttered amongst themselves as they hurried to read and understand the new equations.

  ‘But who did it?’ asked Dr Dalecki.

  ‘I don’t know,’ said Friday. ‘But they’d have to be the biggest genius at CERN.’

  When Friday and Melanie got back to the apartment, Dr Barnes was waiting for them at the door. She was shaking with anxiety.

  ‘What’s wrong, Mum?’ asked Friday.

  ‘Your uncle is here,’ said Dr Barnes. ‘He takes up so much space. It’s distracting me from my work. And he brought a boy with him.’

  ‘A boy!’ said Friday. She hurried past her mother. It was a small apartment. It took three steps to get her to the living room. There was Uncle Bernie. Larger than life. Literally, he was twice the size and weight of a regular man. He was on his feet looking nervous.

  ‘Ian?’ asked Friday.

  ‘He’s okay,’ said Bernie. ‘I found him. He’s going to be fine.’

  ‘Going to be?’ said Friday.

  ‘He had a bit of a knock to the head,’ said Bernie. ‘Er . . . from a fist.’

  Friday burst into tears.

  ‘Oh, please don’t cry,’ said Bernie. He rushed forward to hug Friday. But he was so big and she was so tiny, he wasn’t sure how, so he just patted her on the shoulder. ‘He’s okay. We’ve got him back. There’s no need to cry.’

  ‘I was just so worried,’ sobbed Friday. She grabbed Bernie around the waist and held him tight. Bernie wrapped his arms around her shoulders and hugged her too.

  ‘I know, sweetheart,’ he said. ‘I feel that way about both of you.’

  Now Melanie burst into tears.

  ‘Why are you crying?’ asked Bernie. He didn’t have any more arms to offer hugs with.

  ‘It’s just so wonderful to see Friday finally expressing her feelings for Ian,’ said Melanie. She lunged forward and wrapped her arms around Friday and as much of Bernie as she could reach.

  ‘So where is he?’ asked Friday, a short while later after pulling back and rifling in her pockets for a tissue.

  ‘Well,’ said Bernie. He was nervous again. He didn’t want what he was going to say next to be taken the wrong way. ‘He’s lying down.’

  ‘Where?’ asked Friday.

  ‘In the bedroom,’ said Bernie.

  Friday glanced at their bedroom door. ‘The bedroom here?’ she asked. ‘Our bedroom?’

  ‘Yeah, he’s still not quite one hundred per cent,’ said Bernie. ‘He needs his rest. A lot of rest.’

  ‘What happened?’ asked Friday. It began to dawn on her that perhaps her worries weren’t over after all.

  ‘Well, as I said, he had a bang to the head,’ said Bernie. ‘And it was a hard one. He got . . . er . . . punched in the nose by another passenger on the train.’

  ‘What?!’ exclaimed Friday.

  ‘It wasn’t his fault. Apparently, Ian fell asleep on the train,’ said Bernie. ‘And you know how he’s a good-looking kid?’

  ‘Yes,’ agreed Friday. She and her hormones were well aware of this fact.

  ‘Anyway, there was a girl on the train who noticed too. She kept staring at him,’ said Bernie. ‘Her boyfriend got jealous. And he went over and punched Ian.’

  ‘While he was asleep?’ asked Friday.

  ‘No,’ said Bernie. ‘He woke him up first. Apparently, there was a big fight with lots of wrestling and banging into other passengers.’

  ‘I can’t believe we missed all the excitement,’ said Melanie. ‘I’m going to have to seriously reconsider my policy of always travelling in first class.’

  ‘The guard was called,’ continued Bernie. ‘He broke up the fight and called the police. They were both thrown off the train at Culoz, where the police were waiting at the station to arrest them.’

  ‘So Ian’s been in a police holding cell this whole time?’ said Friday.

  ‘No,’ said Bernie, he really looked pained now. ‘When the police arrested them, they put Ian in handcuffs first. The other guy used the opportunity to get in one big king hit.’

  Friday gasped. It felt like her heart had stopped beating in her chest.

  ‘He knocked Ian out cold,’ continued Bernie. ‘Ian went down like a sack of bricks and because his hands were cuffed, he hit his head hard on the platform. The police took him straight to the hospital. But Ian didn’t have any ID on him. He didn’t look like his description. He wasn’t in a fit state to answer questions. So they couldn’t figure out who he was.’

  ‘Oh no,’ said Friday.

  ‘It’s only when we amended his description and I started contacting police stations at all the stops along the train line that I found him,’ said Bernie.

  ‘That’s terrible,’ said Friday. ‘How badly was he hurt?’

  ‘Physically he’s going to be alright,’ said Bernie. ‘The headaches aren’t so bad and the scans don’t show any permanent brain injury.’

  ‘But?’ said Friday.

  ‘Well . . . he’s a bit . . . foggy,’ said Bernie.

  ‘What does that mean?’ asked Friday.

  ‘What’s going on?’

  Friday turned around. There he was – Ian – standing in the doorway. He was wearing one of her t-shirts, which was too small for him, and hospital pyjama pants. But his face – if she didn’t recognise the voice, she might not have recognised his face. He was transformed. Ian’s hair had been shaved short. There was a big white bandage wrapped around his skull, a cut across his nose with stitches in it, his lip was swollen and split and both of his eyes were puffy and black with bruises.

  ‘Oh, Ian,’ said Friday. ‘I’m so sorry we weren’t there to help you.’

  Ian held her gaze for a long moment. His brow scrunched as if he was trying to think of something. Eventually he said, ‘Who are you?’

  ‘What?’ breathed Friday.

  ‘Ian is doing really well,’ said Bernie in a false jolly voice. ‘He just has a touch of amnesia.’

  ‘Amnesia?!’ said Friday.

  ‘Yeah, he can’t remember some things,’ said Bernie. ‘Although I was hoping he would remember you when he saw you.’

  ‘But you don’t?’ Friday asked Ian.

  ‘Should I?’ asked Ian.

  ‘I’m Friday,’ said Friday.

  ‘She’s your girlfriend,’ added Melanie.

  ‘You?’ asked Ian. He looked Friday up and down. He was apparently deeply confused by this concept.

  ‘Yeah, sort of,’ said Friday.

  ‘No,’ said Ian. He was shaking his head as if to shake off the confusion. ‘But you’re so . . .’ He started rubbing his head.

  ‘Be careful of the bandages, you don’t want to open the stitches,’ fussed Bernie. ‘Maybe you’d better lie down for a bit more.’

  Friday clenched her jaw. She didn’t want to burst into tears again, but she was seriously concerned that her heart was about to break. She watched her uncle lead her boyfriend away.

  ‘This is horrible,’ she told Melanie.

  ‘I know,’ agreed Melanie. ‘Mexican soap operas are fine when you watch them on TV, but you don’t want your real life to start emulating one.’

  ‘What if he never remembers me?’ she asked.

  ‘You have to make him fall in love with you all over again,’ said Melanie. ‘That’s the soap-opera formula.’

  ‘I don’t think I could pull it off twice,’ said Friday.

  Friday had assumed that Bernie would take Ian home to his mother in Paris. But the neurologist had advised against too much travel while his brain was recovering. Ian needed to rest and be still. Interpol had problems in the area that they wanted Bernie to help with so he had to stay too.

  Luckily, it turned out that Uncle Bernie knew Ms Dekker. They’d attended the same security conferences over the years. She was happy to help a colleague when he explained the situation. She arranged accommodation for him and Ian in an apartment in the same building as Dr Barnes. In fact, just across the corridor in the apartment where Friday and Melanie had dumped all Dr Barnes’ rubbish when they first arrived. They found another empty apartment, this time on a lower floor, and moved the trash there so Bernie and Ian could move in.

  Friday was relieved to have the physical work of moving trash. She didn’t know how she was going to interact with Ian if he didn’t know who she was. When Friday finally went to bed, she couldn’t get to sleep. She felt so guilty about what had happened to him. And so hurt that he couldn’t remember her after everything they’d been through. She knew this was irrational. Ian had a serious medical condition. But late at night, in a foreign country, in a strange bed, it is very easy to be irrational. She needed something to distract her.

  When Melanie awoke the following morning, it was to discover Friday sitting on her bed watching videos on her laptop.

  ‘Did you even go to sleep?’ she asked.

  Friday pulled the headphones away from her ears. ‘Sorry, what?’

  ‘Have you been watching videos all night?’ asked Melanie.

  ‘I’ve been researching,’ said Friday.

  Melanie peered around to see the screen. ‘It looks like you’re watching reality TV.’

  ‘Oh, I am,’ said Friday. ‘I’ve been researching how to build a robot warrior.’

  ‘I know I don’t really want to know the answer to this, but I’m going to ask anyway,’ said Melanie. ‘Why?’

  ‘We’re going in the CERN first annual Robot War competition,’ said Friday.

  ‘Again, why?’ asked Melanie.

  ‘So we can be close to the action,’ said Friday.

  ‘The action of the robot wars?’ asked Melanie. ‘You do realise how pathetic that sounds?’

  ‘No, the action of the inter-nerd rivalry that is tearing CERN apart,’ said Friday. ‘The people here are acting more like tribes than scientists. We need to infiltrate their tribal culture if we’re going to get to the bottom of the problems here.’

  Melanie looked closer at the video Friday was watching. ‘You just want to build a robot and play with it, don’t you?’

  Friday smiled. ‘There is an element of that, yes.’

  ‘You nerds are all the same,’ said Melanie.

  ‘Building a robot warrior is a fascinating scientific challenge,’ said Friday. ‘It combines the disciplines of physics, mathematics, engineering and strategy.’

  ‘And crashing whizzy toys into each other,’ said Melanie.

  ‘These robots are much more than whizzy toys,’ said Friday. ‘They’re whizzy toys with high-torque engines and sharpened power tools attached.’

  ‘So where do we start?’ asked Melanie.

  ‘You’re going to like this part,’ said Friday. ‘We’re going to go shopping.’

  Melanie did end up enjoying the day. Friday started at the local toy shop where she picked up a remote-control car.

  ‘That doesn’t look like it could last three seconds in one of those robot battles,’ said Melanie.

  ‘I’m just using this kit for the electronics,’ explained Friday.

  The next stop was a bike store that sold high-torque electric motors. Friday wanted her robot to be fast and responsive.

  Then they went to a hardware store where Friday spent a lot of time looking at shovel blades.

  ‘What are you going to use that for?’ asked Melanie.

  ‘You know Ned Kelly?’ asked Friday.

  ‘The nineteenth-century bank robber?’ asked Melanie.

  ‘His famous helmet,’ said Friday. ‘It was made out of a plough blade.’

  ‘That must have been uncomfortable,’ said Melanie. ‘An adjustable baseball cap can give me a headache if I put the stopper through the wrong hole.’

  ‘In the siege at Glenrowan, Ned Kelly was shot fifty-four times and didn’t die,’ said Friday. ‘That is effective armour.’

  Friday took six shovels, then went to the power-tool section where she bought the most powerful circular saw they had. Or rather, Melanie bought them, using her parents’ credit card.

  The Uber driver gave them some funny looks as they fit all that into the car for the ride home.

  ‘It doesn’t seem right that you can buy so many implements of destruction without some sort of government licence,’ said Melanie.

  ‘I guess they assume gardeners spend so much time in nature that they wouldn’t have any violent impulses,’ said Friday. ‘Or that when they have violent impulses, they act them out on plants instead of people.’

  Friday had a wonderful afternoon putting it all together. She totally stank out the apartment soldering the electronic components together, so Melanie put her foot down when she found Friday researching where she could rent an oxyacetylene torch (she wanted to weld the shovels together). Melanie insisted that they should go down to the local garage and get a mechanic to do it there. This turned out to be a brilliant suggestion.

  Pieter and Hans the local mechanics were bored with servicing family cars and hatchbacks. They loved helping with Friday’s robot. They had some good ideas of their own. Like zip-tying flaps along the sides to stop other robots getting underneath and flipping it over. The mechanics were great believers in zip ties. And they added caterpillar tread so the robot could drive right over the top of another robot if it needed to. By nightfall, Friday had a device that looked like an incredibly dangerous Roomba. It was a solid steel dome with a circular saw spinning from the top like a deadly mohawk.

  ‘All it needs now is a name,’ said Pieter.

  ‘It’s an inanimate object,’ said Friday. ‘Why does it need a name?’

  ‘All robot-wars robots have names,’ said Hans. ‘Usually some sort of play on words. Like Roomboto or Captain Crunch.’

  ‘I’m not good at humour,’ said Friday.

  ‘Then something that describes what it looks like, but in a cool way,’ said Pieter.

  ‘I’m not very good at cool either,’ said Friday. She looked at her robot. She was proud of how well it had turned out. The circular saw looked really menacing. ‘Well, it’s got a saw and it’s a robot, and we’ll be going up against all these PhDs, so how about we call it “Dr SawBot”?’