Despite past friendliness, cattle ranchers Tom and Jim Bledsoe, father and son, fence off their range to prevent its use by neighboring sheep ranchers Tug Wilson and Buck Rankin, suggesting that they hope to end their recent loss of cattle.
Cole Thornton, a gunfighter for hire, joins forces with an old friend, Sheriff J.P. Harrah. Together with a fighter and a gambler, they help a rancher and his family fight a rival rancher that is trying to steal their water.
Retired wealthy sea captain Jim McKay arrives in the Old West, where he becomes embroiled in a feud between his future father-in-law, Major Terrill, and the rough and lawless Hannasseys over a valuable patch of land.
Having been falsely court marshaled for cowardice and sentenced to prison by the Army, Jed Kilton escapes and heads to Nevada Springs to see his kid brother.
A young Eastern lawyer, seriously injured in a stage holdup, secures the help of Hoppy, California and Jimmy in completing his mission to his woman cousin's ranch in Texas.
Muggs and Glimpy, two East Side Kids in the army, return to their neighborhood, supposedly on furlough; actually, Muggs has been honorably discharged with a physical defect, but he tells no one of this.
With a plot line mostly lifted from 1941's "White Eagle", Columbia's 24th serial (following "The Desert Hawk-1944" and ahead of 1945's "Brenda Starr, Reporter"), "Black Arrow" finds carpet-baggers Jake Jackson and Buck Sherman arriving in Blue Mesa in search of gold.
Mamsie catches Lulu making a mess of the kitchen, so she punishes Lulu. When Lulu asks, "How do you know that I made this mess?", the maid says sarcastically, "A little bird told me!" Angered that the bird outside her home snitched to the family's maid, Lulu goes after the bird with her slingshot.