Dangerous virtues. Purity

Purity, Honesty, and Chastity--they are all admirable traits, but when they come in the form of three headstrong, spirited, sinfully lovely sisters, they are "Dangerous Virtues". From the moment Purity lay eyes on the stranger, she feels anything but what her name implies. Who is the mysterious half-breed who has bushwhacked the trail drive she is leading?