Little Prudy's Captain Horace veers from the plan of the first two books of the Little Prudy series. Perhaps in the interest of appeasing a broader readership, the third installment centers on a Horace Clifford, Prudy Parlin's cousin come to visit from Indiana, and with a much stronger focus than Prudy's older sister received in Little Prudy's Sister Susie.

Like boys in general, Horace is a real brat, but has a greater gravity and objective even in his play. Before Horace departs eastward, his father, about to ship off to fight for the Union, gives a striking moral commission to his son. Horace is often inconsiderate and careless, but he certainly works on his virtues by the end, and becomes much nicer. By the end, Horace becomes a decisive, morally significant figure in a way Prudy and Susy were not, and could not have become.

The first two books were moral, but this much more so, for even while Horace is yet a boy, he knows much may yet be demanded of him, if he is to be an honorable son before Captain Clifford, his brave father.