The water of Lake Tana is a bright toffee colour and it slips away on each side of us as the boat slices through it. Pelicans bob about on the surface, and a fish eagle swoops out from the thick dark trees that crown the little island ahead.

There’s a monastery here, one of the few in Ethiopia that women are permitted to enter, and tourists visit nearly every day. My heart sinks when I see the crowd of basket sellers, touts and would-be guides at the landing stage, knowing that my friend and I represent their entire economic opportunity for the day, but everyone is polite and friendly, and no one hassles us when we decline their offers.

It’s hot. We walk up to the 500-year-old monastery between the coffee bushes and I talk to a young deacon, who is no more than 16 years old. He likes being a deacon, he says. He likes the drums and the chanting, the old manuscripts and the gorgeous vestments, but he wonders if perhaps he shouldn’t become an English teacher instead.

His eager voice is achingly familiar. I was a teacher in this country 30 years ago and my students were just like him - slim, energetic and youthfully optimistic. But their optimism didn’t last long. Soon after I left the country, revolution swept out the old emperor Haile Selassie and swept in the dictator Mengistu. Thousands were murdered in the subsequent terror. Tens of thousands more died in the civil war and famine.

I’ve been wondering all these years about those young men who used to shoot their hands up so eagerly in class, and now I’ve got my chance. I’ve come back to Ethiopia to try to find out what’s happened to them all. As well as my students, I want to find the 16-year-old girl who kept house for me, and her baby, whose godmother I became in a dawn ceremony in a Coptic baptistry. I want to find the two young officers of the imperial bodyguard who used to call on me at my house for tea, resting their hands carefully on the knife-edged creases of their khaki trousers, and the little beggar boys who ran after me in the ancient city of Lalibela.

Against all the odds I’ve found two, and I can’t wait to carry on with the quest. I’ve never written a book about real people before, but I’m going to give it a go. And already the stories I’ve uncovered are more amazing than anything I could dream up for a novel.

Elizabeth Laird’s children’s novel, Secret Friends (Hodder), was shortlisted for the Carnegie Medal earlier this year. Her latest novels are Jay (Methuen) and Forbidden Ground (Hamish Hamilton)