The Civil War just broke out and the four characters featured in the previous album will put their rifles at the service of the Union. Chesterfield, Blutch, Tripps and Bryan thus join General Grant's troops where they are immediately assigned to Captain Stark's 22nd cavalry regiment. Their first mission will be to take possession of a bridge guarded by the southern artillery so that Grant can attack with his infantry Lee's troops behind a ridge. But before attacking, Grant asks the sergeant to infiltrate at the heart of the enemy lines in order to judge their strength. Chesterfield accepts. He is accompanied by Corporal Blutch.