Filled with all the action and drama of the West during the Civil War, The Deadliest Gun is a story centered around two teen-aged sisters, Sarah and Katie, whose family has left war ravaged Virginia in 1864 to make a new life in California. Arriving in Arizona, their family is ambushed and murdered by a renegade Union army troop from a nearby outpost, leaving the two sisters to escape to a nearby frontier town. There in the town the two sisters are taken in and cared for by a woman named Catherine, and they begin to make many new friends, while they plan and carry out their revenge for their family's deaths.