This book is a short account of adventures of John Coffee Hays (1817 – 1883), a famous captain in the Texas Rangers and a military officer of the Republic of Texas. Hays served in several armed conflicts from 1836–1848, including against the Comanche people in Texas and during the Mexican-American War. Hays later joined the migration to California, leading a party of a party of Forty Niners from New York that traveled in wagons to California from Texas. Hays was elected sheriff of San Francisco County in 1850.

Hays emigrated in 1837 to San Antonio. Here he had several severe skirmishes with the Indians, and was engaged as surveyor on the frontier. In those times of peril, when Texas needed the assistance of every soldier, Hays could not long remain unnoticed. He was first created captain of a scouting party, and soon after superintendent of the entire border, with the rank of major. Desperate, and sometimes personal encounters with the Indians, soon spread his reputation, and before the commencement of our war with Mexico, he was regarded by the Indians as superior to common men—the bearer of a charmed life.

The following description of the celebrated partisan is given by his friend Reid :

"So many were the stories that went the rounds in camp, of his perilous expeditions, his wild and daring adventures, and his cool and determined bravery, that when we saw the man who held such sway over his fellow-beings, we were first inclined to believe that we had been deceived. But when we saw him afterwards in the field, we then knew him to be the 'intrepid Hays.' So great is his reputation among the Mexicans, that he is everywhere known as 'Capitan Jack.' Notwithstanding his rigid discipline, for his word is law among his men, yet off duty he is a bland and pleasant companion, and the men familiarly call him Jack; though there is that about the man, which prevents one from taking the slightest liberty with him."