Spring is often referred to as the season of love. But for Bob and Helena, two unlikely lovers on the streets of Edinburgh, the solstice is when the magic happens. Midsummer is modestly subtitled "a play with songs," and strictly speaking, that description holds up. This romantic romp from playwright David Greig and songwriter Gordon McIntyre is a straight play peppered with duets, meaning it's not a musical per se. What it is, though, is an almost ridiculously charming piece of theater guaranteed to make you laugh, cry and wish that, like Bob, you had 15,000 pounds in a plastic shopping bag to squander on a pretty girl and a gang of street goths.

Much of the charm in this Third Rail Repertory Theatre production comes courtesy of the leads. Local favorite Isaac Lamb makes Bob much more than simply a lovable loser. Sure, he's a "piss artist" who sells pink convertibles to shady characters and has lengthy conversations with his penis. And, yes, it's true that among his fellow petty criminals he's referred to as "Medium Bob" because he has no defining features. But in Lamb's expert hands, Bob is a hero of romance. Or of romantic comedy, anyway.

And Cristi Miles is perfect as the hard-working, hard-drinking yet vulnerable Helena, who, when not in the courtroom defending down-and-out moms, is busy ruining her sister's wedding by (a) puking in front of the church and (b) accidentally knocking her nephew into the sick. She and Lamb have palpable chemistry, both when they're in bed, having drunken sex with a stuffed Elmo watching, and in quieter moments, many of which are set to song.

While the lyrics aren't always strong, Philip Cuomo's direction makes the most of every moment. Interestingly, the whip-smart script—it delves into everything from Japanese rope bondage to Kim Wilde's current career (she's apparently the gardening correspondent for The Observer)—doesn't dictate which actor delivers which line. That creative freedom could make Midsummer either a director's dearest dream or worst nightmare. Cuomo is obviously in his element, and the pacing, particularly during Bob and Helena's debauchery-filled weekend, is exceptionally fluid.

Midsummer is, without a doubt, a love story. But it's also a rumination on aging, death and how the choices we make shape our fate, for good or ill. So go ahead—make the right choice. Go to this show.

SEE IT: Midsummer is at CoHo Theater, 2257 NW Raleigh St., 235-1101. 7:30 pm Thursdays-Saturdays and 2 pm Sundays through April 19. $20-$27.