Eighteen months ago my daughter Anna left for Canada on a two-year working visa. She had been living in London since graduating from university, and finding city life less and less to her taste. She wanted freedom, room to breathe, new horizons.

She landed in British Columbia and until yesterday we had seen her only once, for a week last autumn, when we flew west, she flew east, and we met in Montreal. She was then about to start a second winter season working in Rossland, a small ski resort in the Kootenays, east of Vancouver and close to the US border.

A few months later, early this year, she decided that she would make a flying visit home during the summer. Our oldest daughter, Sophie, had had a second child, a boy, last autumn whom she had not yet met, while our second daughter Ellie’s first child, also a boy, she had only met when he was a few days old, shortly before her departure for Canada. Her visa would be up in the autumn and she wasn’t sure what her next move would be. Among other things, she didn’t want to leave it too long before seeing the new nephews.

Naturally enough we have missed her dreadfully all this time. The distance seems vast, and although Skype is a blessing, it does nothing to mitigate the knowledge that she’s on the other side of the world. I was thrilled when she messaged me to say that she was planning a visit. But there was a catch: she wanted it to be a surprise for Sarah.

This made me feel anxious. Sarah is not keen on surprises. I am not used to keeping secrets from her. And even were I to agree, I wasn’t confident I’d be able to dissemble for the best part of four months. But Anna was insistent and eventually I agreed. Assuming I could pull it off, the joy of unexpected reunion would be wonderful to behold, and it would surely outweigh any ill feelings Sarah might have at having been kept in the dark.

So we set about making plans. For my part this mainly involved agreeing dates with Anna, then clearing the appointed weekend – a fictitious research trip Sarah and I would make together for the book I plan to start writing later this year. So far so good. Then Anna and I decided that we should also fly Jake, our youngest, up from London for the weekend. He had come with us to Montreal on the first leg of a business trip to California, and we’d spent a wonderfully happy week à quatre.

This was more complicated since Anna wanted it to be a surprise for him also. But by now, somewhat to my amazement, I was starting to relish all this clandestine activity (and becoming a WhatsApp aficionado in the process). A series of messages with Nics, Jake’s partner, ensued. We soon had a surprise rendezvous arranged for him and Anna in London, the subsequent weekend cleared (dog-sitting for Nics’s mother), and plane tickets to Edinburgh booked.

Everything was in place and the day by now fast approaching. Two weeks ago, Sarah and I left for Spain to run a The Stories We Tell course at Cortijo Romero, near Granada. Throughout the week I felt my anxiety mounting. Was this really going to be OK? Was Sarah going to have a heart attack, or be furious with me?

Halfway through the week Anna messaged me for reassurance. She had been speaking to Sophie who thought that Sarah needed some warning. But Anna and I continued to convince ourselves that the full surprise should stand. And I continued to feel anxious. Then came a conversation with Sarah’s sister Jane, in London, whom Anna, by now back in the UK, had also surprised with a visit. Though delighted, Jane was also uneasy about our plans. My anxiety mounted further.

To counter it I visualised the joyful moment. The plan was that I would meet Anna off the train in Edinburgh in time for us to be back at home when Sarah returned from work. I imagined myself greeting Sarah as she got out of the car and telling her that we had a surprise visitor, one she would be very, very pleased to see – just enough to prepare her for a shock without giving it away – then leading her into the house where Anna would be waiting.

Yesterday, Thursday, was the appointed day. On Wednesday, I had spent the day in Edinburgh and returned early in the evening shortly before Sarah got in from running a yoga class. She seemed pensive. Once in the kitchen she told me that she had just bumped into Mary, a neighbour, and mother of Louisa, one of Anna’s oldest friends.

‘Mary said that Louisa is seeing Anna in London next week,’ she said, looking confused. ‘I said it was news to me and was she sure she’d got it right? When I pressed her she looked embarrassed and said that maybe she’d spoken out of turn. I don’t understand. It’s very odd.’

Twelve hours to go. Could I talk my way out of this? My heart raced and the world seemed to stand still. Then I heard myself say, ‘Anna’s coming. Here. Tomorrow.’ I could see Sarah trying to absorb what I’d just said. Twin waves, one of relief, one of disappointment crashed over me.

Mary lives in a different part of the village and now that our daughters are grown up and living away, we hardly ever see her. She happened that evening to be attending a concert in our local arts centre, where Sarah also runs her yoga class. The chances of them bumping into one another like this were remote.

Sarah and I spent the evening talking through the whole deception and ended up agreeing that the encounter with Mary had, in its way, been fortuitous. She wasn’t sure how she would have responded to the surprise and felt that this had given her time to prepare herself. We spoke to Anna, still in London. Though disappointed, she accepted it with good humour.

And by mid-afternoon yesterday we were finally, joyously together. Tonight Jake arrives. The weekend lies ahead. We four will spend it together in love and laughter – and perhaps a little wonder at the mysterious way the universe sometimes has of arranging things.