time passages it was the tale of a soldier on the battlefield of san jacinto , april 21 , 1836-a straggler in sam houston 's army who found himself facing a mexican bayonet ; how he was backed against a tree , begging for life ; and how , in a desperate surge of concentration , he found himself inside the mexican 's body , staring at the empty-eyed creature that had been himself-a creature that gave a convulsive jerk and then lay still .