If you love someone, set them free -- that's the subtext of the most affecting scene in the Round House Theatre's solid production of "Once on This Island," directed by Scot Reese. In the sequence, two elderly Caribbean peasants who have adopted Ti Moune, the show's free-spirited heroine, sadly sanction her planned journey away from home. "Go and find your love / Go and swim the sea / You know where we'll be," sing Mama Euralie and Tonton Julian (Beverly A. Cosham and David Emerson Toney) as the waifish Ti Moune (Montego Glover) gazes away from them, a mercurial mix of stubbornness, terror and heartbreak flitting across her face.

It's a touchingly human moment in a show that traffics in archetypes and Big Themes -- the resilience of love and of nature, the inevitability of death, class struggle, the power of storytelling -- all leavened by piquant Caribbean-flavored music. Frequent collaborators Lynn Ahrens and Stephen Flaherty ("Ragtime," etc.) adapted the work from Rosa Guy's novel "My Love, My Love," a riff on Hans Christian Andersen's "The Little Mermaid" set in the French Antilles.

"Once on This Island" presents its narrative as a tale-within-a-tale: Villagers relate the saga of Ti Moune, who becomes enamored of a man from the island's snobbish wealthy class. Meddling in the affair are the gods of Earth, Love, Water and Death, whose somewhat grandiose presence makes the story feel more like a legend and less like a human drama. What with the musical's speedy pace (a country's social rift, a doomed love affair and many important life lessons, packed into 90 minutes), we're always conscious that we're watching the components of a legend rather than individuals with fleshed-out personalities.

So it's a relief that Glover punches up Ti Moune's idiosyncrasies, her coltish movements and wide-eyed, quicksilver smiles suggesting a shy charisma that might indeed seduce a haughty aristocrat. Glover's voice can be thin in songs such as the yearning "Waiting for Life," but her dancing is more confident, and her crouching, shimmying solo in a pivotal number, "The Ball," adds a bracing jolt of drama.

The other performers function as an effective ensemble, brandishing blue ribbons to evoke a flood, or snapping into rigid postures to depict the island's elite, or impersonating gods and mortals. In particular Toney turns Tonton Julian into an endearing lummox who casts drolly baffled expressions. Griffin Matthews makes a rather enigmatic Daniel; but Eleasha Gamble belts out her numbers richly as Erzulie, goddess of love, and Clif Walker portrays an aptly imperious Demon of Death.

The cast shifts easily into Michael J. Bobbitt's choreography, which tends toward willowy arm gestures and -- irritatingly -- mimelike signifying motions (threshing-type movements to hint at village life, for instance). But the dancing does emphasize the energy in Flaherty's music, with its Caribbean rhythms and spicy percussion (arguably overmiked on opening night).

Designer Daniel L. Conway evokes the milieu with a stylized set: a round stage in front of a tiered walkway and a cane-weave backdrop that's centered on a circle of sea-blue slats. Johnetta Boone's costumes -- tunics and robes in batiklike patterns -- are busier and less elegant, and Martha Mountain's lighting seems overactive. The most artful illumination in the production shines from Daniel's car, which props designer Timothy J. Jones has ingeniously conceived as two headlight-tipped cane poles that a running actor carries under his arms. The effect is so snazzy, you don't wonder that Ti Moune loses her heart to this man.

Once on This Island, music by Stephen Flaherty, book and lyrics by Lynn Ahrens; based on the novel "My Love, My Love" by Rosa Guy. Directed by Scot Reese; choreography, Michael J. Bobbitt; musical direction, Christopher Youstra; set design, Daniel L. Conway; costume design Johnetta Boone; lighting design, Martha Mountain, sound design, Tony Angelini. Approximately 90 minutes. At the Round House Theatre Bethesda, 4545 East-West Hwy., Bethesda. Call 240-644-1100 or visit www.roundhousetheatre.org.

Montego Glover and Griffin Matthews play lovers Ti Moune and Daniel. Below, Glover, Beverly Cosham and David Emerson Toney in "Once on This Island."