It’s sinister how much you can learn from a lost purse these days

Have you ever found a bag or wallet on a train? If so, did you hand it over to station staff immediately – or were you a little more ingenious in your efforts to return it? My guess is your decision might hinge on what you found inside the bag. Did the owner’s name speak to you? Did you feel some sort of talismanic kinship based on a pen or library card? Did you feel overwhelming sympathy for the bereft proprietor?

This dilemma informs the plot of film director Neil Jordan’s new thriller Greta, in which an empathetic waitress (Chloë Grace Moretz) retrieves a smart green leather handbag from a subway train and returns it in person to the rich but lonely Greta Hidbeg (Isabelle Huppert), with alarming consequences.

When I read reviews of the thriller I felt a pang of recognition. Six weeks ago I was on a train heading from Clapham Junction to Waterloo when I noticed a wallet on the floor. I asked the woman sitting near it if she’d dropped her purse, but she said it must have belonged to a passenger who’d just disembarked. So I picked it up, noting the soft black leather and Christian Dior logo.

I hesitated about looking inside, but then thought that if I’d dropped something essential for my day-to-day life I wouldn’t mind a kindly stranger intruding. And, yes, I must admit I’m jolly nosy, too; all journalists are.

I found two bank cards, some cash, train tickets, a card with photo-id of a pretty young blonde woman and – bingo! – a home address. It struck me that it wouldn’t be that hard to track her down. I had her full name and one of her banks was a small outfit and would surely help my woman-hunt. I did ask some Transport for London staff for their advice on the matter and was told that if I handed the wallet over it would take several working

days to be registered at lost property and the cards would be cut up. In other words, the owner would be subject to considerable anxiety and inconvenience.

So I felt free to let loose my inner private investigator. I phoned 118 and established the owner’s parents’ home was exdirectory, then I phoned the woman’s bank and left my contact details, I logged on to Facebook and Instagram, found my target within seconds and left messages. By the time she contacted me I knew, courtesy of social media, what school she’d attended, the names of her close friends and what her dad looked like.

I thought I was being helpful but, seen through Neil Jordan’s eyes, it could all be deemed a bit sinister.

I didn’t diminish my batty middle-aged lady status by suggesting the young woman meet me at a central London venue where I was chairing a talk on FGM. In retrospect, “Do you know anything about infibulation?” might not have been the most reassuring text message to receive from a stranger. In the end she came and sat through the panel, even though I could easily have been a version of the creepy older woman in Greta.

In Jordan’s film, the psychopath is the person who “loses” bags, rather than the finder. But the central question is pretty much the same: why track down a total stranger when it’s not strictly necessary? A potent mix of sympathy and curiosity, I’d argue – along with the fact that smart phones allow anyone to play Sherlock Holmes.

My new friend and I plan to go for a coffee together. But if this were a Hollywood film there’d be strychnine in the pot.