Ida Thornthwaite pushed up her sleeves and scooped a large helping of lasagne onto Kensy’s plate. ‘Well done, dear,’ the woman said. ‘I heard you outsmarted the enemy tonight.’

Kensy nodded, beaming. That meant a lot coming from the single most deadly knife-thrower in the agency. ‘It was about time, really. I was beginning to think I had no strategic skills at all.’

‘I’m sure that’s not true. If you’re anything like your father, you’ll have tactical activities mastered in no time,’ Mrs Thornthwaite said with a wink. She turned to smile at Max, who requested a serving of spaghetti bolognaise and some garlic bread.

‘This looks amazing,’ the boy said, heaping a mountain of grated parmesan on top. He was ravenous. The children were meant to have had a snack before training, but Max had lost track of time in the library, studying a new book he’d found on codes.

Kensy wrinkled her nose at him. ‘Are you sure you wouldn’t like some pasta with all that cheese?’

‘Ha ha,’ her brother replied, but when Mrs Thornthwaite held up her spoon to offer more, he happily passed her his plate. Max inhaled deeply. ‘If this tastes half as good as it smells, I’ll be in heaven.’

‘I couldn’t help myself tonight,’ Ida said, pleased that her efforts were appreciated. ‘After hearing you lot talk of Italy and your upcoming trip, I thought it was only fitting. I haven’t been there since we brought down a scurrilous Prime Minister over twenty years ago, but I just adore the food.’

The twins grinned. The woman looked around and leaned forward. ‘Dame Spencer won’t be happy to see the grocery bill. The price of imported Italian pasta is through the roof at the moment. I couldn’t believe my eyes!’

It seemed strange to think that the elderly cook had once been an active agent. Up until a couple of days ago, when the woman had given the most enthralling lesson on handling all manner of blades, Kensy had only ever thought of her as a grandmotherly figure. Round and squishy, Ida Thornthwaite possessed a smile as warm and comforting as the winter meals she prepared. Kensy now knew better. Mrs Thornthwaite’s skills were lethal.

The twins thanked the woman again and joined their friends, although they had very little time to eat as Miss Witherbee was barking orders to hurry up. The woman reminded Kensy of a greyhound – skinny and angular – but with the temperament of a cranky terrier.

Kensy and Max scoffed down their meals and scampered over to join the tail end of the line of children being ushered from the conservatory via a concealed doorway, which for all the world looked like a wall of mirrors. They headed down a set of stone steps to a passageway beneath the rear courtyard and into their classroom in the bunker under the stables.

As to be expected, this was no ordinary teaching space. For a start, there was a complete absence of desks and chairs. Instead, the room was arranged in the style of an amphitheatre. The children’s names were lit up on the riser where they were required to sit and, to date, their seating arrangements had changed each time so that they never sat next to the same person twice. On the opposite curved wall was a huge screen that the teachers had used several times now during lessons. Willow Witherbee was sitting in a single chair close to the door.

Mr Nutting, resplendent in his customary navy-and-red tracksuit, stood in front of them. A three-dimensional plan of the maze appeared between him and the children, floating a metre from the ground. Max had worked out it was a hologram that was somehow projected from below, but he was yet to understand the finer details.

The teacher scratched at the side of his nose and zipped up his jacket. Kensy noticed that, for a man whose face was still youthful, he had more than his fair share of grey hairs. It was probably stressful being a teacher and even more so working undercover as an agent.

‘Shall we take a look at how things played out tonight?’ Mr Nutting began. ‘As always, I want you to think strategy and where you went wrong.’

Avatars of each one of the children appeared inside the hologram of the maze. The students leaned forward in their seats, eager to get through the activity as quickly as possible. It had been Harper’s birthday yesterday and the girl had leftover treats that she’d promised to share once they were in their dorms.

‘Can you see your mistake, Sachin?’ Mr Nutting pointed at the avatar of Alfie with a long wand-like implement that shot a glowing beam from its tip.

Sachin grimaced as he watched Alfie take him out at almost point-blank range within the first minute. ‘I was too busy looking for Max, sir. I wasn’t paying attention to anything behind me,’ he replied. ‘And I might have been thinking about who was going to be our opening batsman in the upcoming Melbourne Boxing Day test.’

There was a titter of giggles from the other children as Gordon Nutting shook his head. ‘Well, in this business you need laser focus and eyes in the back of your head. There is no time to be daydreaming about cricket.’

‘Yes, sir,’ Sachin said meekly.

The man was about to continue when he caught sight of Inez and Yasmina whispering in the back stalls. Gordon pointed his wand towards them, a red dot centring on Inez’s forehead bang on one of her freckles. It took a few moments for the girls to realise that everyone was staring at them.

‘What?’ Yasmina said, before spotting the glaring sign on her friend’s brow. She pressed her forefinger to her lips and swallowed.

Inez looked around. ‘Do I have something in my teeth?’ she asked.

Carlos shook his head. ‘I don’t think so, but Mr Nutting might be about to kill you with his laser pointer.’

The children laughed and Inez shrunk down in her seat.

‘You’re lucky I’m not in the mood for blood tonight, girls.’ Mr Nutting sighed. ‘Now, could we please get back to the task at hand?’

The footage continued and there were several times the teacher sped up the action. Kensy tapped her foot, wishing he would play the whole thing on fast forward. She really wanted to get back inside and find her uncle before he went out. Miss Witherbee also seemed eager to be on her way. She had stood up from her seat and positioned herself by the door.

‘Let’s run through the last five minutes to see what led to the ultimate demise of Sachin’s team,’ Mr Nutting said. ‘Actually, perhaps you would like to take the children through this section, Miss Witherbee.’

All eyes turned to the woman, who was glued to her phone. She was smiling to herself and seemed far, far away.

‘Earth to Willow,’ the man said, not bothering to hide his exasperation.

The ripple of laughter from the children roused the woman.

‘Sorry,’ she said, her cheeks flushing. She dropped her phone into her pocket and straightened. ‘What did you say, Mr Nutting?’

‘Forget it,’ the man muttered, and proceeded to walk the room through the final part of the exercise before firing questions at the children about what they could and should have done differently. He praised Kensy’s quick thinking and flexibility to get herself to the tree and then invited the group to offer some alternative scenarios.

Carlos was the first to volunteer. He had been watching the playback carefully and had devised a plan where he could have covered Dante if only they’d thought to work together. He moved the figures around in the maze with a swipe of his hand and, seconds later, the outcome was completely different, with Kensy being the one who was shot. She also fell out of the tree, which garnered guffaws of laughter.

Kensy rolled her eyes and resisted the urge to rub her shoulder. ‘Gee, thanks, Carlos. That would have hurt.’

Mr Nutting asked for another version of events and this time it was Max who put up his hand. Kensy eyeballed her brother, trying to send him a telepathic message to make it quick, but it seemed that he had reimagined the entire evening and come up with several ways their team could have finished off the others in half the time it had actually taken. To his credit, his ideas were pretty amazing. Even Mr Nutting was impressed.

It was just after nine o’clock when the children were dismissed and, although they were bone-tired, the twins set off in search of their uncle. Kensy shivered as they wandered the halls, having left her coat back in the classroom. But the man was nowhere to be found. It was probably for the best given the twins could barely keep their eyes open. When Mim said she’d seen headlights on the driveway, they gave up the search.

The twins made their way down a long corridor towards the back door. At least two metres wide, the passage housed a range of ornate antique furniture, including bureaus and sideboards, a grandmother and grandfather clock and a rather startling brown bear standing on its hind legs and baring its very pointy incisors. Song told them his name was Frank and he’d been a pet many years ago, when it was a fanciful trend in Victorian England to keep exotic animals. Apparently, the creature had romped about the gardens like a faithful hound and was known for his placid temperament. But Kensy and Max’s great-grandfather had decided that, in death, Frank might prefer to be a little fierce – hence the stance and sharpened teeth.

‘What did you think of Uncle Rupert?’ Kensy asked.

Max shrugged. ‘I think I should reserve my judgement until we’ve spent some more time together.’

‘He was only kidding around – what he said about me being the fun twin,’ Kensy said, giving Max a jovial elbow to the ribs.

‘He doesn’t even know us,’ Max said indignantly. ‘And I can be as much fun as you when I want to be.’

Outside, an eerie mist had settled over the courtyard.

‘Do you think anyone would notice if we slept in the house tonight?’ Kensy said. She wasn’t keen to trek back to the stables in the gloomy weather. The thought of her queen-sized bed and feather-down quilt – not to mention that enormous claw-foot bathtub – was far more tempting than the narrow bunk alotted to each agent-in-training, the shared bathroom and incessant snoring. Then again, there had been the promise of Harper’s leftover birthday treats.

Max didn’t have time to answer as Song appeared from behind a potted palm, where he had just reclaimed Wellie and Mac’s latest bone stash.

‘Good evening, Miss Kensington, Master Maxim,’ the butler greeted them, a huge bone dangling from his left hand. ‘I would strongly suggest that you return to your colleagues this evening. You are on an official training camp and it would not do your service history any favours to skive off, especially on the last night.’ His face softened and he pushed his glasses back from the tip of his nose. ‘Besides, I thought you were enjoying the company of your peers.’

‘We are,’ Max said, and looked at Kensy. ‘At least, I am.’

Kensy nodded. ‘I am too. It’s just miserable out there and I left my coat in the classroom.’

‘I can show you another way,’ Song said with a twinkle in his eye. ‘It is much warmer.’

The twins were suddenly wide awake. ‘Is it a secret tunnel?’ Kensy asked. The girl was certain Alexandria had only given up a fraction of its secrets to date. Every day there were new discoveries to be made – extra rooms, endless passageways and subterranean lairs.

‘It is my favourite secret tunnel,’ Song said.

Although Kensy and Max now had their own beautiful bedrooms on the first floor of the house, for the duration of the training camp they were bunking in with everyone else in the stables. Located to the left-hand rear of the mansion, the magnificent Victorian structure had once housed an exquisite collection of steeds but had been converted into accommodation many years ago now. It provided sleeping quarters for the entire Pharos student body and at least six of their teachers, who stayed in the private suites at either end of the long corridors. While the estate still retained working stables and an equestrian centre, they were situated on the other side of the village.

The girls’ dormitory was at one end of the building and the boys’ was at the other, separated by a large sitting room in the middle with comfy couches, a cinema, pool and table tennis tables, a sumo boxing ring complete with suits that had the children hysterical with laughter anytime it was used, an electronic dart board as well as an array of board games and books. It reminded Kensy of the games room in the cellar where Song had entertained them for hours during their first visit – except there was no bowling alley here. There was, however, a flying fox, which launched from the gallery above and sent the children pummelling towards a pit of foam bricks at the other end.

Rows of bunk beds lined the walls of the dorm rooms, with large bathrooms in the corners containing six showers and toilets. They also had a pulley system, which former students had rigged up years ago, allowing them to trade midnight snacks, not only in their own dorms but between rooms as well. These days they used a drone, which was far more efficient as long as someone remembered to open the doors. Kensy was sleeping on the top bunk right by the entrance with Autumn below. Yasmina and Harper were beside them.

Song led the children through to the back of the kitchen and yet more rooms they’d never seen before – there were larders and pantries and a huge door that looked like the access to a bank vault.

Kensy’s eyes lit up. ‘Is this where Granny keeps her real treasures as opposed to all the junk upstairs?’

Song frowned and arched his left eyebrow. He turned the small device in the centre of the door this way and that, listening for the clicks, then spun the giant wheel. Kensy and Max peered into the darkness. The butler flicked a switch and beckoned for the children to follow him. Then he stopped and the twins realised that the floor beneath them had started moving.

‘Whoa.’ Kensy grabbed hold of her brother in an effort to steady herself. They were on something akin to a travelator you might find at an airport.

Max laughed with incredulity when he saw what else the passage contained. Concealed lighting illuminated an array of artworks. ‘It’s a gallery!’ the lad exclaimed.

‘These are the most valuable works in Dame Spencer’s collection,’ Song replied with a nod.

Kensy peered at a three-dimensional study in coloured pasta. ‘That’s my name on there,’ she said, having no recollection at all of making it. They glided towards the next masterpiece.

‘I remember painting that in second grade in Banff.’ Max shook his head. ‘Thank goodness we’re going to be spies because, if Granny ever thought we were potential artists, she must be sorely disappointed.’

The children marvelled at the display and noticed that there were plenty of their father’s and uncle’s endeavours too. Rupert’s were actually quite good – particularly a self-portrait Song told them he’d created for his A levels.

‘It’s lovely that Granny thinks these are worthy of being framed,’ Kensy said. ‘Most parents throw them out after they’ve been on the fridge for six months.’

Song clasped his hands behind his back and nodded. ‘Your grandmother has kept everything.’

‘I don’t know if that’s cute or creepy,’ Max said with a smile.

A set of six intermittently spaced spiral staircases appeared in the distance.

‘Now, I just need to remember which is which,’ Song said. He tapped his fingers on his forehead for a second then clapped his hands, bringing the travelator to a standstill. ‘This is your exit, Master Maxim,’ he said, pointing to the second set of stairs. ‘It will take you up to your dorm room. Once you are inside, it will be impossible to release the hatch from above, so do not get any ideas about exploring with your friends after lights out.’

Max said goodnight and scurried away. As he stepped on the fourth tread from the top, a panel opened above his head. The boy emerged from the middle of the floor and narrowly missed being clobbered by a football Alfie had kicked across the room. The boys were stunned to see him. Just like Song said, as soon as Max was through, the hatch closed and was completely invisible to the naked eye.

‘Okay, so which one’s mine?’ Kensy said.

Song scratched his head. He always got this wrong, although he wasn’t about to admit that now. It was bad enough that, one night many years ago, he had accidentally directed a young agent-in-training into the headmaster’s quarters. The man was in the middle of his evening yoga session, mid headstand, when the hatch lifted and catapulted him against the wall. The headmaster had leapt to his feet and thwacked the unsuspecting girl with a karate kick to the torso before he realised his mistake. ‘There,’ Song said, pointing to the second staircase from the end and clapped his hands to make the footway move again.

As they drew close, Kensy leapt off and rushed to the top, hoping the girls hadn’t eaten all of Harper’s treats already. She scrambled up and out, ready to be the centre of attention. As the trapdoor closed, however, it dawned on Kensy that this wasn’t her dorm room at all. She took in the smaller space with its canopied double bed and roll-top desk. The decor was more in keeping with the main house and there were several lamps and a cosy-looking armchair in the corner too.

‘I don’t know why you couldn’t have waited for me,’ a woman whined over the sound of a running tap. ‘I would have loved to escape for the night.’

Kensy recognised the voice and gasped. She raced towards the door, wincing at the sound of the floorboards creaking beneath her feet. The bathroom tap stopped and she heard the doorknob turning. Panicking, Kensy dove under the four-poster bed and held her breath.

Willow Witherbee walked out of the bathroom and looked around. Kensy could see her feet and the hem of her dressing-gown coming closer and closer until she could have reached out and touched the woman’s painted toes.

‘Sorry, I thought I heard something,’ Willow said. ‘Honestly, if any of those kids come banging at my door in the middle of the night, I am going to pretend to be dead.’ She paused. ‘It’s okay. Shugs is on it. First thing.’

At the mention of that name, a shiver ran down Kensy’s spine. Despite Fitz assuring her that it couldn’t have been Shugs who had abducted her and Max in London, she was convinced he was wrong. She just had to find a way to prove it.

Annoyingly, Kensy was stuck under the bed for almost an hour. Willow Witherbee was in and out of the bathroom another four times before she finally hopped under the covers – except, not a minute later, she sighed and was up again. When the symphonic explosions rang out from the bathroom, Kensy was seized by an equally violent fit of giggles she was sure would blow her cover. The girl clamped her hands over her mouth and tried to think zen thoughts. If there was any accompanying smell, she was done for.

‘Oh dear,’ Willow said out loud as she climbed back into the bedroom. ‘No baked beans for you tomorrow morning, young lady.’

With commendable effort, Kensy managed to regain her composure and waited an eternity until the woman finally switched off the lamp and began to snore. She then slid out from her hiding spot, crawled across the floor and turned the doorhandle, only daring to breathe once she was safely on the other side.