Bloomsday: Reaching out for something to hang onto when time gets slippery.

G. K. Chesterton, in his poem The Ballad of the White Horse, famously wrote that “The great Gaels of Ireland are the men that God made mad, For all their wars are merry and all their songs are sad.” That might help to account for the feeling of Steven Dietz’s Bloomsday, which finishes its run at North Coast Rep this weekend. The promo copy understandably uses the words “winsome” and “lyrical” to describe the play's story about Robbie, a young American man visiting Dublin because his girlfriend has broken up with him just before their planned trip to London, and Cathleen, an Irish lass who is leading a tour that traces the wanderings of the central character in James Joyce’s novel Ulysses. And the Rep’s featured quotes from other critics call the production “whimsical” and “charming” — again, understandably.

Given all that, it might come as some surprise to learn in the early going that the man is beset by a profound interior coldness that winds up haunting him throughout his life, while the woman is terrified that she will end up following her mother into the madhouse, on account of the way time slips out of place for her. It’s a neat trick to sing such a sad song and still get people use such cheerful adjectives to describe it, especially when the play opens with, and depends on throughout, just the sort of time slippage that portends doom for our heroine. Robbie — or rather Rob, as his 55-year old self is known — arrives on stage and asks us to really look at, to really see, 20-year old Catherine, who is soon to meet his own younger self. But he’s not here on a stroll down memory lane, observing what is to become his defining day (he’s gone on to become a teacher of Ulysses, and while he doesn't love the book, he knows it by heart). Instead, he is, impossibly, a participant, and wastes no time in engaging Catherine in conversation and telling her things about her future meeting with him — even though he knows this is what terrifies her. (How does he know? Because she’ll tell his younger self later that day.)

It’s something of a nightmare scenario. But it doesn’t feel like it, because that’s not how the actors play it, and their performances are, strangely, both breezy enough and strong enough to keep the horror and heartbreak from sinking in. The song they sing is upbeat and quick-tempo, delicate and playful. When, later on, grown-up Cait (as she comes to be called) meets up with young Robbie, she shrugs that “it used to trouble me, the shifting,” before noting with pleasure that “you and I at these ages are a pretty good fit.” She has a point: Robbie is no fan of the future, since his previous girl ditched him when she decided that he wasn’t serious enough about it, and Cait has finally made peace with her deeply painful past, starting with the day she found and then lost him. (Besides accepting her great sorrow, she has also found places to put her beloved dead, so that they cannot unsettle her. Mad Ma is in a chair by the south window; Angry Dad is safely behind a door.)

And so it goes: Rob meets Cathleen, Robbie meets Rob, Cait meets Robbie, Cait meets Cathleen, Robbie meets Cathleen, and finally, Rob meets Cait. The youngsters are surprised to interact with their older selves, even incredulous. But they never pause in acting out the drama just as Rob and Cait remember it, and they’re never so thrown that the music skips a beat. Not even when Robbie's trouble with the future bumps up against Catherine's tendency to time shift.

The play’s title is taken from Dublin’s annual celebration of Joyce’s novel on the day when it is set, June 16, and Ulysses makes its way into the proceedings in various places and in various ways — including the bittersweet ending. Rob declares that he would keep seven words out of the book's many thousands, spoken by a dead man being lowered into his grave: “Wait. I wanted to. I haven’t yet.” “It’s all right there,” he concludes, wistfully. (Another w to slip in alongside "winsome" and "whimsical.") “What’s done is done,” answers Cait. “Best not to think about it.” But the music doesn’t end on that pat conclusion, not quite. Instead, the final note hangs in the air, as if defying both the sad past and inevitable future. A neat trick.

• Bloomsday, by Steven Dietz
• North Coast Rep, 987 Lomas Santa Fe Drive, Suite D, Solana Beach
• Directed by Andrew Barnicle, cast: Martin Kildare, Rachel Weck, Hunter Saling, Jacqueline Ritz; scenic design, Marty Burnett; costumes, Renetta Lloyd; lighting, Matt Novotny; sound, Aaron Rumley; stage manager, Aaron Rumley.
• Playing through February 2, Wednesday at 2 pm and 7 pm, Thursday and Friday at 8 pm, Saturday at 2 pm and 8 pm, and Sunday at 2 pm.