After a year in California, Grouard's wife returned to the South Pacific with two of the children, leaving Benjamin with the middle son, Frank.

In 1855 he was adopted into the family of Addison and Louisa Barnes Pratt, fellow missionaries for the Church of Jesus Christ of Latter-day Saints with his father.

[14] For seven to eight years he lived in the camps of Sitting Bull and Crazy Horse until he managed to escape, becoming an emissary of the Indian Peace Commission at Red Cloud Agency in Nebraska.

[17] General George Crook and his officers, having retreated from the Rosebud, were hunting in the foothills of the Bighorns when Grouard, known to the Brulé as 'One-Who-Catches' and to the Hunkpapa as 'Standing Bear',[11] was acting as guide.

Between 9 and 10 in the morning of June 25, 1876 Crook's forces were in Goose Creek Valley when Grouard saw the smoke from Indian signal fires in the distance, which indicated that George Armstrong Custer's command was engaged with the enemy, outnumbered, and being badly pressed.

The officers present used their field glasses but could make no sense of the smoke signals and laughed at the idea that a half-Indian could have such knowledge of their meaning.

[10] To prove that he was right, at noon Grouard mounted his horse and rode towards the signals, reaching the Little Bighorn, a distance of some seventy miles, at 11 pm on June 25.

Here he discovered the bodies of the slain before being chased back to Goose Creek by hostiles, bringing the news of Custer's death to Crook.

[10] In August 1877, officers at Camp Robinson received word that the Nez Perce of Chief Joseph had broken out of their reservations in Idaho and were fleeing north through Montana toward Canada.

When asked by Lieutenant Clark to join the Army against the Nez Perce, Crazy Horse and the Miniconjou leader Touch the Clouds objected, saying that they had promised to remain at peace when they surrendered.

Frank made a quick stop at the wounded outlaw who was being attended to by one of the spectators, saw that he was still alive, then proceeded upon a fourteen mile chase for his partner, who ended up escaping.

However, Frank had suffered permanent eye damage from the snow and frost, and spent the rest of his life "consult[ing] eminent specialists concerning his eyesight."

[31] The actor Bruce Kay, who appeared only five times on screen between 1955 and 1958, played Grouard in the 1958 episode, "The Greatest Scout of All", on the syndicated anthology series Death Valley Days, hosted by Stanley Andrews.

In the story line, the half Sioux Grouard is caught in a culture clash but becomes a highly regarded scout for the United States Army, who is dispatched on the toughest of assignments.