The quest will become available after completing the previous mission Exhuming and Other Innocent Pastimes in Red Dead Redemption.
Return to Coot's Chapel to Seth and start a dialogue with him. The old man, as usual, is robbing graves. The old madman plans to take the bodies to a quiet, secluded place and continue searching for the treasure map. Get into the wagon with the man and follow the marker to the southwest. On the way, bandits will attack you. Shoot back at them and continue moving to the designated place. Upon arrival, let Seth go about his business. The mission is completed, and as a reward, you will receive +37 points in the Fame category.