By Duncan Macmillan. Directed by David Mackay. Presented by Mitch and Murray Productions. At Havana Theatre on Tuesday, December 3. Continues until December 14

Lungs is smart and often very funny. But the characters can also be annoying, so go for the acting.

In the show’s opening moment, M and W are standing in the checkout line at IKEA when M suggests that they might consider having a baby, and W, his female partner, panics. There we have it: the show is about a couple of Gen Ys stumbling toward adulthood.

It’s a tough slog because they are neck-deep in paralyzing self-consciousness, a state that’s heavily inflected by the impending disaster of climate change. When W considers the tonnes of carbon dioxide that a new life would unleash on the planet, she moans, “I’d be giving birth to the Eiffel Tower.” The couple’s grinding efforts to be good—or to see themselves as good—are often risible: “We support the smaller coffee shops against the larger chains.” And playwright Duncan Macmillan skewers the arrogance of their principled stasis: referring to procreation, M and W agree, “We can’t just leave it to the people who don’t think.”

Much of the script’s comedy is about how to act; its deepest darkness is about how to love. Simply put, W is an emotional bully who’s desperate to be topped and M is a doormat. In fact, W is just this side of lunatic. She won’t shut up: every thought that passes through her mind also passes out her lips. Complaining that M is objectifying her when they have sex, she says, “Sometimes, it looks like you’re about to hack off my limbs.” Then, a split second later, she notices he’s hurt and reverses herself: “I don’t know what I’m talking about. I never feel that way.” M clings to W like a mistreated dog clings to an abusive master and, like a dog, he’s not above sniffing a stranger’s crotch. They’re both so selfish and unformed that, at times, I questioned why I was spending time with them.

But maybe they’re just young. And I hung in for the acting, which, under David Mackay’s direction, is outstanding. Newcomer Stephanie Izsak, who plays W, is an artist to watch. Here, her every reaction is skinless and unpremeditated, and she handles W’s speeches, which are long and full of tricky rhythms, like a veteran. In one of the most impressively unadorned performances I’ve seen from him, Kayvon Kelly provides a perfect counterpoint—baffled, angry, and loving. On a bare stage, with no set or props to fall back on, both are fearlessly, relentlessly present.

I attended a preview performance. The acting was already top-notch. It’s only going to get better.