The Rangeland Avenger by Max Brand

Through the branches of the copse in which she was hidden, the girl saw the sun descend in the west, a streak of slowly dropping fire. And now she became excited.

"As soon as it's dark," Arizona had promised, "I'll make my start. Have your hoss ready. Be in the saddle, and the minute you see us come down that trail out of Sour Creek, be ready to feed your hoss the spur and join us, because when we come, we'll come fast. Don't make no mistake. If you ride too slow we'll have to ride slow, too, and slow ridin' means gunplay on both sides, and gunplay means dead men, because the evenin' is a pile worse nor the dark for fooling a man's aim. You'll see me and Sinclair scoot along that there road, with the gang yellin' behind us!"