The Alamo, 1836, Texan revolutionaries under the command of Barret Travis are holed up inside the Alamo, a Crumbling mission in San Antonio, supplies are running low, Travis gathers his men and scrapes a line in the sand, Travis told his men that if they crossed over the line and stayed with him, they would probably die, and anyone that wanted to leave, could go. Only one man left.
on the cot is Jim Bowie(inventor of the bowie knife) he was to sick to stand, and had to be carried across the line.
Fourth wall, Although it hasn't been proven that Travis drew a 'line in the ground'
he did inform his men of the danger and offered a chance to get out.