Penney has done an excellent job of tying the history of the gypsy population to a missing person’s mystery even as her novel threatens to run ashore in the midst of a real slog. The distrust, unrest, and hidden expectations are palpable in The Invisible Ones as London private detective Ray Lovell investigates the Jankos, a family of gypsies who have cobbled together a hand-to-mouth existence in a West Sussex trailer park.

Alternately narrated through both Ray and garrulous teenager JJ, Penney’s human drama centers on handsome Ivo Janko, whose wife, Rose, mysteriously vanished back in 1978 and was rumored to have run away with “a gorjio.” As the novel opens, we see the Janko clan dreaming, desperate for a miracle cure for young Christo, who has been afflicted since birth with a mysterious disease called the “gypsy curse.”

Tene, the family patriarch (and JJ’s great uncle) remains tight-lipped about the poisoned, dark blood of his family, which he mostly views as diseased and incestuous. Tene and Ivo were the only witnesses to a number of strange and tragic events that occurred several years ago, while the specter of Rose’s disappearance trails after them like a “wolf in the shadows.”

Rose’s father, Leon Wood, sees Ray the perfect fit for the inquiry into the whereabouts of his precious daughter--mainly because Ray is also part gypsy. Leon is convinced that Rose was murdered. Ray knows all too well what it’s like to be called a “dirty gyppo." He’s familiar with the long, petty battles over caravan sites, the evictions and petitions, and the mutual distrust that has kept Leon from going to the police, a distrust that quietly ferments beneath Penney’s ambiguous novel.

The Jankos are “old -style Travelers” in the real sense of the word--not house gypsies living semi-settled but wanderers who can’t settle in bricks and mortar, constantly moving on from lay-by to farmers' fields. While JJ is left tormented with the quaking emotional landscape of a young boy hungry for connection, Ray is reeling from his recent divorce, often blinded by feelings of hopelessness and sadness that threaten to derail the investigation.

The novel plays with time, place, and the order in which events played out back in 1978. But Penney’s prose often feels weighty as it shifts and twists, threatening to slide out of reach and into an exercise that resembles pulling teeth. From rumors of poisoning to the discovery of bone fragments in a pit called the Black Patch, the author heaps on incidences in a plot boiling over with drama and coincidence.

While the tale eventually unfolds the Jankos' terrible, scarring secret, the story lacks tension with its plot that lulls you into a false sense of security. What could have been a nostalgic account of gypsy life becomes something much darker: the intrusion of the contemporary existence set against blood and culture, and the myths of a lifestyle on the brink of distinction.