In the early 1800s, many black slaves in the southern states began to risk their lives to gain freedom in the North. They escaped from plantations with no money to buy food and no maps to help them find their way. They could travel only at night. If runaway slaves were caught, they could be beaten to death. Still, many slaves tried to flee. Slave catchers chased them, but the runaways seemed to disappear into thin air--or through a secret underground...