A cancer scare is the catalyst for a family reunion in this week’s A Play, A Pie and A Pint at the Traverse. In recovery from a mastectomy, well-to-do solicitor Rachel has to call on her estranged, down at heel cousins, Marion and Josie, to warn them to get their BRCA2 gene tested. At the same time as performing these familial duties, she has to pick up her career again under the management of her married boss, Alex, with whom she’s having an affair.

Writer Ann Marie Di Mambro leavens this sombre sounding premise with comedy from the salt-of-the-earth Glaswegian sisters, Marion and Josie (Julie Coombe and Isabelle Joss). It’s often at the expense of their stuck-up cousin Rachel, but sometimes we’re simply laughing at their bare-faced cheek and lack of pretension. Most definitely, despite the life-threatening shadow of cancer, this isn’t a sobfest.

But when it does get serious, it sets about its business very deliberately. There are passages of unnatural factual explanation about the benefits of catching cancer early and other complications from BRCA2 genes. These are transparently aimed at informing the audience, rather than anything which would emerge spontaneously between the characters. It plays more like Theatre in Education than standard drama.

It also turns out cancer is a plot device to set up the real tension – the class conflict between the female cousins. It’s a familiar rich meets poor scenario, but Di Mambro makes it work through well-observed clashes of two cultures, like Rachel’s casually superior forgetfulness of her cousin’s names, and Marion’s pinpoint baiting of her snooty cousin. Coombe and Joss make a very watchable and realistic double act, with bold, confident performances. As a character, Rachel’s buttoned-upness makes her harder to love, but Shonagh Price carries it well.

The men get short shrift; underwritten, even as bit players to a female led story. There’s hope for Alex (Richard Conlon) at the start. He seems to have extra dimensions and inner conflict – compassion for Rachel, alongside his selfish philandering. By the end, though, he’s just reduced to a penis on legs, this otherwise intelligent lawyer delivering comedy lines about being turned on. Josie’s unseen husband Kevin isn’t even afforded that, written off as a bad’un off stage via one-sided phone calls and gotcha pictures of him having an affair. They’re shallow fodder for the central buddy-up between the women. More often a failing with the genders reversed, of course, but two wrongs don’t make a right.

So while it’s enjoyable for its comedy moments and the satisfaction of seeing family divides slowly bridged, Rachel’s Cousins comes with other trappings that are less convincing.