When General Grant asked for help from General Alexander, he decided to send him Blutch and Chesterfield. The 22nd cavalry regiment had to recompose itself following an assault by Captain Stark and the general did not like the inactive soldiers. When they arrived on the spot, the two soldiers of the Union discovered a seat that was engulfed and two units to take the city of Petersburg ideally defended by the Confederate forces. Two units that hated each other, more so, one consisting of whites and having an alcoholic as their leader, and the other composed of blacks who did not enjoy having a white commander. A situation for the least desperate. It was then that a young lieutenant-colonel, Pleasants, proposed a saugrenuous idea: to dig a tunnel in an old mine that would allow to blow up enemy lines from below. Blutch and Chesterfield then found themselves with a shovel and pick in hand and begin their long excavation work...