The next morning, I'm up at the crack of dawn having tossed and turned most of the night through wacky dreams. In one, I led visitors through the castle dressed as an 18th century woman who looked suspiciously like Claire Randall, while Jack stood in the ramparts wearing a kilt, waving a sword around and warning us to go nowhere near the Standing Stones outside. In another, the castle crumbled around us and Jack pounced on top of me to save me from falling bits of masonry. I was just enjoying the feeling of his weight crushing me and wondering if that was indeed what I thought it was when Little Ms Mena woke me up with a loud yowl, fed up of having to wait so long for her breakfast.

Jack had given me one of his branded Highland Tours tee shirts to wear, though because he had only spares ones to fit Sam, it is far too big. I belt it around the waist and do the whole make-up so light it looks like you're not wearing anything wondering afresh on why it takes you twice as long as when you plaster it on, and stand outside to wait.

Bang on seven am, the bus pulls up and Jack throws the door open. "Jump in. The tee shirt looks much better on you than it does on Sam."

Belted up, I run through everything I found out about Doune Castle during last night's impromptu history lesson. "Historians think the original was built in the thirteenth century, though the present-day version sprung up in the fourteenth, built by the Duke of Albany, who also ended up as the regent of Scotland, though his son came to a nasty end of the headless variety. It later became the property of the Earls of Moray, and it saw military action in the seventeenth and eighteenth centuries, the latter during the Jacobite risings," I rattle off, delighted I've managed to remember it all.

"Fantastic," Jack nods approvingly. "My guide book for it is old, but it might interest you to know that latterly, the castle's been used for the filming of Outlander."

"What!" the squeal far too loud for a confined space.

That special grin lights up his face, making his eyes sparkle and his skin gleam. "I thought you might like that. 'Course, I never play on the fact I look a teeny-tiny bit like Sam Heughan when I take visitors there." At that, he winks. Stop that, my inner conscience yells at him. When your blasted eyelid closes, your other eye and the rest of your face does this thing where it appears to invite me to a private party. You've got an ex you're clearly not over so please keep your winks to yourself. My conscience says this all fiercely. My subconscious begs him to wink at me again—and this time slowly, a lazy drop of the eyelid and lashes, a tiny lift of the outside corner of his mouth and the slight puckering of lips that transfix my attention, wondering what they would feel like on mine.

As we seem to be in friendly mode, I risk a personal question. "Sorry to be so nosey, but why don't you and the doctor have the same surname?"

The air changes and I worry I've made a mistake. The arms and shoulders that hang over the steering wheel tense up. If I flicked them with my Doune Castle guidebook, they might shatter. Then, he lets out a sigh and I see the muscles of his upper body relax. "My mum left my father when I was ten," he says. "He used to beat her up. And Mum remarried twelve years ago. A guy called Ranald McLatchie, who owns a big farm a few miles west of here."

"And you," he says, "seeing as we're in getting to know you mode, why did you break up with your fiancé?"

I never told him Ryan was my fiancé, which leads me to conclude he asked someone. I give him the abbreviated version, gratified when he laughs at the helium balloon. We've arrived at the pick-up point for today's tour and I realise Jack's questioning of me allowed him to avoid having to answer anything more himself. Neat.

"Gaby! So great to see you!"

I'm no sooner out of the bus when I'm embraced in a massive hug. "When we saw it was to Doune Castle, John Junior here and I could not resist." Darcy, America's most enthusiastic Scottish fan export, has turned up, kitted out in Wellington boots, a fur gilet and a thick waterproof overcoat. She also waves a pair of sunglasses. Scottish weather, she tells me, is not as reliable as Arizona's. It's best to come prepared for anything.

Thanks to Jack's quick tutorial, I know a lot about Doune Castle's recent history as a filming location. Darcy, John Junior and the eight other avid Outlander fans listen as I relate what bits of the castle were used and how the film crew built an entire eighteenth century style village in its grounds. Then, Darcy takes over as she and the other visitors discuss Outlander Book 1 scene by scene, and give their considered opinions on all the actors who play the characters in the series. This takes us all the way to the castle where the sweeping drive-way and long approach finally silence Darcy. They squeal with excitement, however, as we recognise the spot where they re-created the old Highland village.

Much to my relief, everyone opts to pay extra for the audio tour, meaning I don't need to remember any of my castle facts. They switch their headsets on and faces light up—Sam Heughan did the voice over, Jack tells me, so all the Outlander fans will delight at having him talk in their ears.

"Do you want a look around?" Jack says as they all head off, heads tipped back to stare at the stone walls that tower over us. How can I resist? My own little tour of the castle accompanied by Jamie Fraser. "Only if you call me Sassenach?" I say, and he nudges me. "As if. Come on then. You might recognise the kitchen."

I do, though I'm disappointed to discover the crew recreated it in a studio rather than filming it at the location. Jack's a brilliant guide. He points out things of interest, but doesn't bombard you with information. And he keeps us away from the visitors we've brought here, moving us in and out of rooms just as they leave or arrive. At the top level, we can see for miles around—trees, water and the nearby village. "I bet lots of people have tried to paint this," I say, and he nods. "Probably not as easy as all that, capturing all the different shades of green."

He rests his forearms on the wall and I admire the way the sun catches the brightness of his hair and sets his profile sharply against the sky behind it. "You're right by the way. I think I need to go down the Outlander route with the tours. I advertised this one as Doune Castle where Outlander was filmed and it sold out in minutes. Would you design me some Outlander stuff for my website? I'm happy to pay for it."

I bite back my immediate response, "No charge! I'd do ANYTHING for you, Jack!" That's one job I don't mind doing for free, but I decide it'll sound unprofessional and too much like I fancy him if I offer to waive the fees.

"You two are so adorable," Darcy has found us and she waves her phone. "I gotta get a picture of you both. I swear it's Jamie and Claire come to life. Throw your arms around her Jack. We might as well make this seem like the real thing."

I mutter feeble protests, but Jack is game. I will Darcy's phone to break, so she needs to yell for John Junior to bring the back-up phone; anything to prolong the heavenliness. Jack's got one of those rock-hard bodies—the one I gave him in my imagination. But it's warm and comforting at the same time. He drapes his arms around my shoulders and his head rests next to mine. I wouldn't need to twist that far for my lips to be within kissing distance. Darcy takes plenty of photos but it's all over too soon and Jack releases me and tells the group they must get back to the bus if they're to make the next stop on the agenda in time.

"What's your number, Gaby?" Darcy asks as we make our way back towards the bus. "I'll send you one of the pictures, the one I've just put on my Facebook page. Ten people have asked me already if I've just met Jamie and Claire! I didn't think you looked like her but other people obviously do."

When Jack drops them off for a late lunch at the coffee shop in Deanston, I sneak a glance at the picture on my phone, blowing it up so the screen shows only our faces. Wow. It's striking how happy I look. The big grin Jack wears might just be for the camera but it lights up his eyes too. The similarity to Claire Randall, or the actress who plays her anyway, isn't that obvious apart from me having curly brown hair and blue eyes too but if Darcy's Facebook friends only saw a small version of this on her news feed, maybe they'd take me for her.

Everyone seems delighted with their day by the time we drop them off at five pm. And Darcy promises by the time she's told all her three and a half thousand Facebook friends what an incredible experience Highland Tours provides, Jack will be booked out from now until 2050. "If God spares him," John Junior adds, the first time I've heard him speak. He says the words solemnly but his eyes dance. A dry sense of humour is probably a necessity if you live with Darcy.

Tourists dropped off at the hotel, Jack and I have another thirty minutes alone together. I rack my brains, trying to think of either questions that don't sound too nosey or stuff that make me sound witty and fun. I'm still dying to find out the whole Kirsty story, but I daren't ask.

"How's the cat sitting going?" he asks. "Must be a huge relief not to be sneezing so madly every time she comes near you. Kirsty used to let Mena sleep in the bed. She'd plonk herself on my chest and not move. Kirsty thought it was cute. She was always taking pictures of me in bed, Mena on top of me and posting them on Instagram. I didn't like it; the pictures made me look like I loved myself."

I battle conflicting emotions—the sharp pierce of jealousy when he puts 'Kirsty', 'bed' and him in the same sentence, and elation when he admits Kirsty's pictures of man and cat drove him mad. Not a mistake I would make, I promise myself. I'd be far too excited by the prospect of having him all to myself to want to share it with the world.

(Though perhaps I'd take one picture to show Katya. She's my best friend, and she deserves details.)

"Little Ms Mena is fine," I say, "especially now I've discovered what cat food she likes. It's the most expensive cat food you can buy, but much cheaper than smoked salmon and organic chicken breast." We have about five miles to cover until the Lochalshie sign comes into view. Can I segue the Mena chat into Kirsty questions?

"I'm sorry you and Kirsty broke up," I say, fingers crossed behind my back for such a blatant lie. "She seems such a lovely person." Toes crossed too.

"Are you," he says, eyes firmly on the road in front. Statement or question? Words that say I'm sorry too or I couldn't care less? "I don't know if..."

"Yes, yes," I jump in and the words babble up, nonsense and rubbish. "So kind to want to help people all over the world find love, even when your own heart is broken into smithereens." Did I really say that? "And then there's the new blog too, where everyone will find out the best ways to get a commitment—"

I have said far too much. The bus slams to a sudden halt outside Kirsty's house.

"A new blog?" he asks, his voice incredulous. "What's the title?"

"Ah, I don't know. I've probably got it wrong. Could be a blog about home decor. I mean, judging by this house she's an expert of how to do that well. Home decor blogs are all the rage at the moment. After diet blogs of course. That could be the perfect combination couldn't it? How to use wall-papering and paint to help you lose weight, so you get slim and fit at the same time as upping the value of your house three times or whatever. I should suggest that to her."

I trail off, aware I've lost my audience. He's practically drumming his fingers on the steering wheel, waiting for me to get out of the bus.

I unclip the seat belt and open the door, turning to face him. His face remains staring at the road ahead.

"Um, thanks Jack. I enjoyed today. If you want me to help out again...?"

He stirs himself. "No, you did a great job. Really helped me out. Thanks Gaby."

And with that, he drives off leaving me with the sinking realisation that the Katya voice that sounded in my head just there shouting at me to stop talking was too late. Rearrange these three words, Gaby, into a sentence that sums up what you've just done. Blew. I. It.

Inside the house, Mena comes running. "Hello, little Scrumptious!" I haven't referred to myself as 'Mummy' yet, but it's only a matter of time. Mena will be comforting this evening. She and I can curl up on the sofa once more to watch Outlander Series 3 again and I can tell her having an unrequited crush on a TV star is much easier on your day-to-day well-being than having one on a real-life person.

The phone rings as soon I as I finish feeding Mena. Kirsty, and I hear her sharp intake of breath when I say I've spent the day on a bus tour with Jack. I decide keeping silent on his reaction to the blog news will spare me further sighs.

"You did the guide tour for him?" she says, her voice rising to a pitch at the end, and I squirm.

"Yes, but only because it was an emergency."

"But this is counter to my plans," she declares indignantly. "Did you talk about me? Mention the bad boy billionaire?"

"Yes. He looked sad." Oops, Gaby. Not one lie but two. Distraction needed. "Did you see those pictures I posted of Mena online?" Part of the deal with the cat sitting service is that you upload pictures on the website so owners can check in with their pets. I've discovered the truth of the old saying, never work with children or animals but Mena finally obliged me yesterday by a) looking super cute, and b) staying still long enough for me to get a good picture. Then, I managed a short film of her jumping up as I dangled bits of chicken over her.

"Mmm-hmm. I hope that was organic chicken. Anyway, the brilliant news is that part one of my plan has worked—the ten steps to commitment process I'm going to trademark and publish on my website."

Part one, it turns out, is that pictures of Kirsty and the bad boy billionaire are all over the Internet. They don't touch, but he shoots her adoring looks in a lot of the shots.

"Um, don't you like the bad boy billionaire?" I ask. It seems an obvious solution.

"That's not the point. Anyway, please can you make sure you have the pictures on your screen the next time you're in his house and he's there too? And can you get me Dr McLatchie's phone number? Jack listens to his mother, so the next stage is for me to cultivate that relationship again and she'll start dropping my name into conversations with him."

I put the phone down a few minutes later, dazed. Somehow, I've been bamboozled into agreeing to do everything Kirsty asked for. But plans and processes don't work if you're trying to get someone to date, or re-date, you, do they? As ever, that painting appears in front of me, the colours shimmering and Kirsty's eyes pinned on me. No-one who's been offered as much as five and a half thousand pounds for a painting keeps it if it doesn't mean a great deal to them.