"As my life has become fuller, my gang of friends has become smaller" … Chrissie Swan.

"I didn't want boring and I certainly didn't get it" … Chrissie Swan. Photo: Julian Kingma

Most of us are good, most of the time. Apart from the person who invented the Milk & Cookies Milky Bar, who is inherently evil.

I like to believe that people are generally wonderful. But sometimes good people do bad things. Like me, for example. When I was in my late 20s, I was the other woman. But before you strike me off your Christmas-card list, please consider that it was a total accident.

How did he decide to do this? Had he done it before? Was I a moron? 

I had met a charming lawyer - let's call him Matt - at a barbecue, where we'd hit it off like a Weber on fire over a few sausages-in-bread and a nifty pasta salad. Matt lived in the country, which was great for me as I wasn't up for a full-on relationship that involved spending nights on the couch in trackies watching Hey Hey It's Saturday. I didn't want boring and I certainly didn't get it.

Things progressed quickly and, between my job as an advertising copywriter and my fabulous single life, we'd meet at my flat, which resembled a two-storey garage, for clandestine grease and oil changes. It was, to say the least, exciting. But it never occurred to me to ask why he'd always answer my calls (only ever to his mobile - alarm bell No.1: no home phone) within the first ring, and there was never a chance to leave a voicemail message. Ever. He didn't have the option (alarm bell No. 2: no voicemail). It would just ring out instead.

One night I was at a friend's party and I had a missed call from a private number, which I knew would be him (alarm bell No. 3: silent numbers). I excused myself from the third round of Midori Shakers and called him back from outside the pub - only to be surprised when a voicemail message kicked in. "Hi! You've called Dave ... and Clare. If you have an inquiry about your tax return something something something ..."

I didn't hear the end of the message-bank greeting because I'd passed out in the gutter. Or maybe it was the sound like a kettle whistling on my eardrum that muffled the end of it.

He was married. His name wasn't Matt. He was an accountant. The single lawyer called Matt I'd been seeing for a few months was actually a married accountant called Dave. Ten minutes later, he called me back after having seen two missed calls from me. Clearly oblivious to the fact he'd activated his identity-revealing voicemail greeting, the conversation started cheerily enough.

Matt/Dave: "Hey, gorgeous! Are you having a good night?"

Chrissie/Idiot: "Yeah. It's all right ... but not as exciting as hanging out with a married accountant called Dave."

Matt/Dave: Click.

He must have hit a weird reception patch or gone through a tunnel. At home. Because his phone immediately dropped out. And I never called again. I really wanted to, because I wanted the nitty-gritty. I was sleepless with questions. How did he decide to do this? Had he done it before? Was I a moron? How many others had been hoodwinked? Did his wife know? Could he do a good deal on my tax return?

I'd have vivid dreams where I'd confront him and abuse him with clever arguments for which he had no answers. The lack of closure sent me mad. Armed with his true identity, profession and the town he lived in (the only piece of his story that checked out), I was able to track him down and see where he lived and worked. And I drove there.

Before you start calling Glenn Close's management and asking her to play me in a biopic, consider that I really had no clue as to why I was in the car with the street directory opened on a page with lots of white and green bits leading me down a highway I'd never been on to a place I'd never heard of. I think I just wanted to see something real.

I got to his street and drove past his house, where a pretty blonde was helping two kids out of a car. So there were kids, too. I didn't see that coming. It made me so sad for them. What sort of a man was this? I contemplated doing a U-turn and telling her to run. That her husband was a liar and a narcissist and perhaps her whole life was a lie. But it wasn't really my place, was it? I drove away.

To this day I wonder if that was the right thing. Would I want to know if my husband had been up to this? I care deeply about the sisterhood and would do nothing to make a woman and mother question what she believed was true and real in her life. But does keeping her husband's secret make me complicit? Or should I have told her and watched what meant nothing to me and nothing to anyone, in the scheme of things, destroy the lives of many?

* All names have been changed.

Was Chrissie right to keep quiet, or would you have told Matt/Dave's wife what he'd been up to? Have your say and vote in the poll on the Essential Baby forum.

Chrissie Swan is the co-host of Mix 101.1's breakfast show in Melbourne and 3pm Pick-Up nationally. She's also on Twitter.