The story behind this week's Oran Mor play, Thank You, it transpires, could form the script for a play in itself.
Writer Catrin Evans came up with an idea for a play in which two former college student lovers meet up after 20 years and revisit their relationship.
And it's an interesting enough premise.
But then when the play was cast, with Colin McCredie and Lousie Ludgate in the lead roles, the writer discovered the two actors had in fact lived together – when they were college students.
"I play Mike and Louise plays Ella, the anxious couple who meet at a busy train station," reveals former Taggart star Colin.
"We discover that Ella has contacted Mike via Facebook, after all this time, and suggested they meet up in this out-of-the-way neutral venue.
"It's a sort of Brief Encounter in reverse, given the relationship is in the past, but we have no idea why Ella has asked to meet Mike."
Indeed. Confrontation. Revelation. The stuff of suspense and drama. Could she be about to reveal Mike is the father of a child he knew nothing of? Is it more complex?
"What we discover will surprise the audience," says 40-year-old Colin. "It's something completely different."
The actor maintains the very clever play is about memories.
It's about what we thought we were like 20 years ago. It's about discovering what other people thought of us a long time ago.
It's also about how sexual politics have changed; men are now being accused of actions which back in the seventies and eighties were treated far more lightly.
"A recent example is the Julian Assange accusation," says the actor. "There has been a whole debate recently about sexual morality and the issue of permission and that's the sort of case which may never have made it into court a generation ago."
Father-of-two Colin says the play is harrowing; it raises dark issues. But it's not without laughs.
He said: "There are funny lines in this play, and this audience at Oran Mor responds so well to a hint of comedy. It's got a sense of Harold Pinter and David Mamet about it."
The actor, who starred recently in I, Tommy, the Tommy Sheridan bio-play before going on to appear in panto in Dunfermline, maintains Thank You is the hardest piece he's worked on.
"It's because there is repetition in the play," he says.
"A lot of the lines are quite similar because you are talking again about a same incident, although referenced in a different way.
"And this is tricky for an actor; you hear the lines then use them to take you on to the next part of the story but you can get confused thinking 'Is this the first time I've said these lines or the second?"
He adds, laughing: "There's a real potential for skipping 10 pages of the play."
Yet, Colin admits he's not only enjoying the challenge of the play, there's an added delight in appearing alongside Louise.
"We shared a flat 20 years ago when were both at drama college," says Colin of his stint at RSAMD in Glasgow.
"We didn't go out as a couple, but we have that background of knowing each other really well all that time ago.
"It all helps us put ourselves in the situation the two characters find themselves in."
He adds, smiling: "The play delves into the sexual history of the pair. And if I didn't know Louise so well there may have been an awkwardness to get over. But because we know each other so well we have a shorthand between us that really helps."
But what was it like living with Louise? "It was mental," he says, grinning at the recall of student life in a flat above the King's Cafe in Elmbank Street.
"There was another girl in the flat as well."
Two girls and a boy? It's the seventies sitcom, Man About the House, all about sexual politics, unrequited lust and whose turn is it to empty the bins?
"Yes, I was Richard O'Sullivan, but entirely unthreatening," he says, grinning.
"And I have to say I really liked the set-up. I like the company of women more than men – and they both used to make my tea, for which I'm eternally grateful."
l Thank You, Oran Mor, until Saturday.