How was buck kidnapped and sold to the man with red sweater?

Unknown to Buck, he is in danger. Manuel, a gardener's helper, has amassed a large gambling debt. His salary can barely support his large family, and there is little left to help him. One night, when the Judge and his sons are gone Manuel takes the unsuspecting Buck on a walk. They arrive at a flag station where a man is waiting for them. Money changes hands, and Manuel ties a stout rope around Buck's neck.