Max rubbed his sleepy eyes and pushed himself up against the pillows. It took him a few seconds to remember where he was and that it was Christmas Day – the first he’d ever spent apart from his parents. Although he’d always cherish last night’s celebrations, Max would have given anything for his mum to be sitting on the edge of the bed and his dad goofing around in the background. Just to hear their voices would be the best gift ever.

With a sigh, Max slipped out of bed and walked to the window. He pulled back the heavy drapes as Kensy barrelled through the door in her dressing-gown and slippers, carrying a large parcel. She dumped it onto the bed and crash-tackled him with a boisterous hug. ‘Happy Christmas, little brother.’

Max grinned. ‘Happy Christmas, big sister by thirty minutes,’ he said, smoothing his hair.

Kensy took a deep breath and stepped back, wiping her eyes. ‘Before you say anything, I’m not crying, okay? We know Mum and Dad are fine – fine enough to keep in contact, anyway – and I’ve been thinking about their message. They said “ciao”. Doesn’t that mean “bye” in Italian? Do you think they were hinting to their location? They could be in Italy, Max.’

He’d had the exact same thought, though he hadn’t planned on sharing it with his sister, knowing how prone she was to being hasty. ‘It would certainly be ironic if they were,’ Max conceded, ‘with us travelling to Rome tomorrow on the school History tour.’

‘We should get word to Fitz!’ Kensy exclaimed.

‘Steady on, Kens,’ Max cautioned. ‘We don’t know for certain that’s where they are – we’re only guessing.’ He fetched a beautifully wrapped gift from the desk and handed it to her. The paper was made from a white pearlescent stock and bordered by prancing reindeer with glittery red noses and flanks flecked with gold leaf. Song had helped the boy to source it from the Burlington Arcade, the man’s favourite stationery shop in London.

Beaming, Kensy grabbed the parcel with both hands. She held it to her ear and shook it vigorously, eliciting a grimace from her brother. ‘Wait, I got you something too,’ she said, and scooped up Max’s gift from where she’d abandoned it on the bed. ‘Sorry, I’m not very good at wrapping.’

The Santa-patterned paper was crumpled and torn in places where the girl had clearly encountered difficulty. Kensy appeared to have used several rolls of sticky tape and undertaken the task wearing oven mitts. While she wouldn’t win any prizes for presentation, Max appreciated the effort.

Kensy tore the paper off her present and was surprised to find another box to open. Max, meanwhile, took his time hunting for the end of a piece of sticky tape. Kensy lifted the lid and pulled out a gilded birdcage with two miniature robins inside it. One was sitting on a swing and the other was on the floor. Kensy held it up and examined it closely, turning the object in her hands until she spied the mechanism.

‘Oh, Max, it’s an automaton! It’s like Granny’s elephant downstairs but tiny.’ She wound the key and gasped as the birds began to flitter and chirp. The one on the floor flew up and around the cage while the other did loops on the swing.

The boy grinned at her. Max knew she would be itching to pull it apart to see how it all worked. ‘Promise me you’ll leave it in one piece for today at least.’

Kensy wrinkled her nose. ‘Only if you insist. You know I’ll put it back exactly as it was – if not better.’

Max nodded and finished opening his present. He was awestruck when he realised what it was. ‘How on earth did you manage to get this?’ he asked her.

‘Fitz and Song helped me. We found it in an antiques shop on Portobello Road,’ Kensy said proudly. ‘It’s way better than the bag of rocks you collected for me when I was six, that’s for sure.’

‘Really?’ Max laughed at the memory, and it felt good to remember happier times. ‘I thought you loved them. Dad said they were magic.’

‘Magic my eye.’ Kensy shook her head. ‘I believed anything back then.’

‘You should consider that payback for the handle you unscrewed from our bedroom door and tried to convince me I could use as a portal to another world the Christmas before.’ Max placed his gift onto his lap and began tapping away on his very own enigma machine. It was a contraption invented by a German engineer, Dr Arthur Scherbius, at the end of World War I. Said to be the most sophisticated cipher machine ever developed, it looked much like a typewriter but used a series of rotors and electrical currents to randomly assign a code. During World War II, a clever Englishman called Alan Turing managed to crack the German’s cipher. It has been said that Turing’s work shortened the war by two years and probably saved over fourteen million lives.

Kensy returned the automaton to its box and walked over to the window. ‘Have you seen the garden yet? Autumn said it would snow. It’s beautiful . . . Mum and Dad would love it here.’

In the early-morning light, the estate sparkled. The lollipop trees along the top of the wall closest to the house looked as if they’d been dusted with icing sugar, and the Atlas fountain was frozen solid. Autumn had only told Kensy the week before that the fountain was another one of the estate’s treasures, with a strongroom beneath it containing yet more secrets to be discovered. Apparently, none of the junior agents had ever been inside – it required top-level security clearance – so they weren’t even absolutely sure it existed. Kensy couldn’t wait to investigate further.

A line of black taxis could be seen heading for the main gates. Kensy frowned, not recalling anything in the itinerary about off-site activities this morning. She hoped they hadn’t missed an important instruction. While it wouldn’t have been unusual for her, it would be highly out of character for Max. She didn’t have to wait long to find out as her train of thought was interrupted by a knock on the door.

‘Good morning, children, and a very merry Christmas to you,’ Song said, entering the room with a bow. Unlike the twins, who were still in their pyjamas, Song was dressed in his customary black dinner suit. Over the past few days, the butler had donned a variety of outfits ranging from casual clothes to last night’s ugly sweater. It seemed a bit glum now that he was back in full work mode – especially today.

‘Happy Christmas to you too, Song,’ Max said.

‘Where’s everyone going?’ Kensy asked, pointing out the window.

‘All will be revealed in due course. Your grandmother wishes to see you in her suite,’ Song replied. ‘I cannot tell you any more, Miss Kensington, no matter how hard you try to get it out of me. Not even if you bought me the complete collection of Johnny Cash for my Christmas present.’

Kensy giggled. ‘As if that would ever happen.’

Max shrugged on his dressing-gown and slippers and together the children followed Song to their grandmother’s suite. The butler gently tapped on the door and, after a generous pause, ushered the children inside, where they found Cordelia on the phone. She mouthed her apologies and gestured for them to make themselves comfortable. Max noticed that she was also still in her pyjamas, which he found oddly comforting.

‘Thank you, Gabriel, and a very happy Christmas to you and the family,’ she said warmly. ‘Oh, and please tell Catherine I’m looking forward to seeing her at the fundraiser next week. Goodbye, dear.’ Cordelia put down the phone and sat back with a sigh. ‘Sorry, darlings. The Prime Minister doesn’t like to be ignored.’

Kensy and Max smiled wryly at one another. Of course their grandmother would be exchanging Christmas greetings with the Prime Minister of England. Didn’t everyone? Max had been gobsmacked to read some of the cards that had arrived from dignitaries around the world. Among them had been a beautiful hamper sealed with the royal warrant, which had been sent directly from Her Majesty. Cordelia held out her arms and the twins rushed into them.

‘Where’s everyone off to?’ Kensy asked. She couldn’t help but feel she was missing out on the fun.

‘A major mission went live late last night,’ Cordelia said, stifling a yawn. ‘It appears that those who wish to do the world harm do not have any consideration for public holidays or celebrations. It’s to be expected, I suppose. Quite a few of our guests left straight after the party and everyone else is setting off now.’

Kensy’s chest tightened. ‘Does it have any thing to do with Mum and Dad?’

Cordelia shook her head. ‘A world leader is in peril, along with several hundred thousand civilians should our people fail.’

Kensy felt a pang of relief followed by a stab of guilt. She was glad her parents weren’t involved, but so many other people’s loved ones were. All of a sudden it didn’t feel much like Christmas.

‘Has everyone gone?’ Max asked, already knowing what the answer would be.

Cordelia nodded and touched his chin. ‘I’m afraid you’re stuck with me and the household staff,’ she said with a wink. ‘The operation is all hands on deck for now. Your friends and teachers will, however, be on your three o’clock flight to Rome tomorrow.’

‘Why couldn’t we go on the mission? We’re ready,’ Kensy huffed. She immediately remembered who she was speaking to and looked down at her slippers, chastened. Although Cordelia was their grandmother, she was also the head of Pharos and important enough to receive hampers from the Queen. It wouldn’t do her cause any favours to behave like a stroppy child – even Kensy knew that. It was just so frustrating to be mollycoddled all the time. She was burning to be able to help.

‘Oh, darling, we don’t ever use the children on assignments unless we absolutely have to,’ Cordelia said.

Kensy bit her lip. ‘So, we’re not up to scratch?’

‘I didn’t say that at all.’ Her grandmother raised an eyebrow. ‘You are both doing incredibly well, but, believe me, fieldwork is not for the faint-hearted and you have years of excitement ahead of you. Besides, I wish I was going to Rome with Mr Reffell – the man’s a walking history book. You’ll have a wonderful time.’

‘Granny’s right,’ Max said. ‘We’ve only just started training. What if we messed up? We could endanger a lot more people than ourselves.’

Kensy rolled her eyes. ‘Anyway, let’s not sit around and mope,’ Cordelia said, springing to her feet. ‘I think there might be something special for both of you under that tree over there and after lunch we’re going to deliver gifts to all of the children who live on the estate – and take dinner for their families too. We can’t let Mrs Thornthwaite’s feast go to waste.’ Cordelia’s phone rang. ‘But I think there’s someone who’d like to wish you both a happy Christmas first.’ She lifted the device so the children could see the caller.

‘Fitz!’ the twins gasped. Kensy pushed in front of her brother, who had to manhandle her to the side so Fitz could see them both.

He was clearly holding the phone in one hand away from his face – although every now and then he forgot and they had an up-close image of the inside of his (very clean) nose. ‘Hi kids, are you having a good morning?’

Max took the phone from Cordelia and held it out in front of him.

‘Where are you?’ Kensy asked. ‘Have you found –’ She stopped and checked herself. ‘I mean, happy Christmas.’

The children chatted to Fitz for several minutes, regaling him with all the stories from the night before. He said he’d heard about their accident too and was very proud of the way they’d handled themselves. When their grand mother left the room to check on breakfast, they told him about their latest message from their parents.

‘Have you found anything?’ Max asked. His eyes searched the screen for clues as to the man’s whereabouts, but all he had to work with was the image of Fitz standing in front of a window covered by a sheer curtain.

Fitz shook his head. The twins told him about everyone leaving and what the day had in store. Max also thanked him for helping Kensy find the best present ever. Just as they were saying their goodbyes, the curtain behind Fitz flapped in the breeze and the sun lit up the view. The children could see a silhouette of rooftops and a large dome.

‘You have a great time in Rome,’ Fitz said with a smile. ‘And I’ll see you soon. I promise.’

Once the call had ended, Max looked at Kensy, a glimmer of hope in his blue eyes. ‘Perhaps sooner than we think.’