A Melodramatic Escape Into the Clutches of the Enemy : HOUSE ARREST by Mary Morris; Doubleday $22.95, 271 pages

See the girl tied to the railroad tracks. See the smoke of the onrushing locomotive. Hear Snidely Whiplash laugh.

For all its subtlety and control, Mary Morris’ fourth novel, “House Arrest,” involves us in a primal melodrama. A New York-based travel writer, Maggie Conover, visits a Caribbean island--Cuba in all but name--and is detained by the authorities, who pressure her for information about a woman she met by chance two years ago: Isabel Calderon, dissident daughter of the dictator, nicknamed “El Caballo.”

Conover is lodged comfortably in a hotel but forbidden to leave the premises. She can call home, but the phone is tapped. She is interrogated, sometimes in menacing prison compounds, by a polite cop, Major Lorenzo, and by others with “the kind of eyes that make you understand that one human being can actually pull out the fingernails of another.”

Calderon has disappeared, it seems, and they think Conover helped her. This at first appears absurd, to her and to us. Conover’s job is updating tourist guidebooks; her brief acquaintance with Calderon had nothing to do with politics.

But later, as “House Arrest” flashes back to Conover’s childhood and to her previous visit to la isla, we begin to wonder. “I’ve always needed a secret life,” she says, after growing up with a controlling father and a timid sister. Even now, happily married, with a 5-year-old daughter, she finds domesticity restrictive and needs to “go on these junkets three or four times a year and in this way get my taste of freedom. My fix.”

As the flashbacks continue, we see that Conover’s interest in Calderon was anything but casual. They are complementary opposites--Calderon flamboyantly liberated in lifestyle but unable to leave the island; Conover free in the political sense but feeling herself confined. Their relationship takes on erotic overtones. They swap clothes and seem to want to exchange identities.

Eventually, Conover’s narrative undermines its own premises. How can we take seriously her initial disclaimer that “for reasons that I cannot understand I have found myself at times in circumstances that others would consider to be extraordinary”? Given what we come to know about her and Calderon, she has no right to be surprised that the authorities want to question her. So why did she come back?

See the train schedule tucked into the girl’s bloomers. See the wild light in her eyes. Did she--egad!--somehow connive in Snidely’s tying her to the rails?

Morris (“Nothing to Declare,” “A Mother’s Love”) doesn’t mean for us to lose sympathy for Conover, but she does create a complex protagonist who is much more than a victim.

Besides being a thriller, “House Arrest” is a meditation on themes of freedom and captivity. Conover and her husband, Todd, install a home security system that makes them feel trapped rather than safe. Calderon, the only daughter among the dictator’s swarm of illegitimate children, can’t avoid hearing his voice on TV or radio in every house she passes. Her mother, Rosalba, remains bound to him by love and admiration for his revolutionary ideals. The aging El Caballo himself is a prisoner of his public role. A frog shut in Conover’s hotel bathroom croaks for release--echoing the yearning of la isla’s human residents.

In the end, this novel, despite its suspense and exotic detail, isn’t a melodrama so much as a story about melodrama’s eternal, escapist appeal--the temptation Conover feels to “just lose yourself somewhere in the world, to go away and never return, and only the few people you’ve left behind . . . would ever really think about where or why you’ve gone.”