Being caught, bloody gun in hand, leaning over the body of the man he had threatened to kill forces bronc-buster Glenn Crawford to turn up at the Big O ranch, a weary, footsore fugitive with more than one score to settle.

Even the murder of the ranch owner in San Antonio had not prepared Crawford for the state of affairs he finds at the ranch. His sudden presence there seems to scare some of the crew half to death and lead others to try to kill him every chance they get.

For the moment, however, Crawford is more interested in the state of affairs in his own body than in those of the Big O and the murderer he is sure the ranch harbors. A veteran of the saddle, Crawford discovers that since an accident which he suspects was planned, he goes into a frenzy of pain and trembling panic whenever he gets near a horse. But in spite of the torture it costs him, Crawford stays on at the ranch. He knows he cannot be a free man until he finds the murderer of Otis Rockland. Nor can he be a whole man until he conquers the black devil of a killer horse, Africano. After he meets Merida Lopez, an exotic beauty whose presence at the Big O is surrounded by mystery, he has a third motive for staying around, although he stands to lose his reason if not his life.

Trapped by forces which he cannot understand, and half-crazed by the torturing pain and panic which he tries desperately both to overcome and to hide, Crawford gets himself more and more hopelessly entangled in what, as old Delcazar points out, looks like the most dangerous thing that ever hit the wild brush country. Crawford is offered a strange proposition by sinister Dr. Huerta; he listens to Merida's spellbinding tale of Santa Anna's chests—and as he listens, the jagged third of a map he possesses, plus a dying man's painfully gasped out words, take on a new and important meaning; he waits, trapped, weaponless, for a killer to come nearer, nearer—And he delivers to his other pursuers the body of one sent out to kill him—only to become more deeply enmeshed in new and still more terrifying trouble. Crawford's irritation at being stirred by Merida, whom he alternately respects and suspects of playing him for a fool, doesn't prevent him from riding secretly with her in the night in search of a place so malicious few men have ever stepped foot in it. Nor does it later prevent him from risking an agonizing death to follow her into it.

Before the true murderer reveals himself, and before Crawford can again call himself a whole man, much violent action takes place. Set against the exciting background of the untamed Texas border country, this is a thrilling brew of suspense, quick death, adventure, and love.