Final answer:
Walt decides to help Loren Hall escape the dangerous Stampeder/men by securing a horse and clothing for a discreet departure from Utah. They face a slim chance of escape due to the vigilant pursuit of their adversaries and the overall perilous situation.
Step-by-step explanation:
When Walt decides to help Loren Hall, they are facing a dire situation in which they need to escape the Stampeders/men. This escape is necessary due to the threat posed by these men, who are likely rustlers or outlaws, and the dangerous environment they are navigating, which is evident from dramatic scenes involving the white herd stampeding and the perilous conditions in Surprise Valley. In their plan to flee from Utah, Walt has to secure a horse and less conspicuous clothing for Hall to aid in their discreet departure. The risks are high, as mentioned, because there's only 'one chance in a hundred' to make it through due to the vigilance of the Stampeder's pursuit. They hope to leave behind the violence and start anew, which is underscored by Lassiter's wish to put away his guns and become a regular man in a place where they won't be hunted.