This week we're bringing you a story from our friends at History This Week, a podcast from the History Channel.

April 3, 1951. A man who escaped slavery is grabbed off the streets of Boston and thrown into a carriage. He fights back, shouting to the crowd, but it doesn’t matter. Under a new federal law, even the North isn’t safe.

The Fugitive Slave Act has turned cities like Boston into hunting grounds. Freedom seekers are being captured, and ordinary citizens are being forced to help.

But across the North, resistance is growing. In Pennsylvania, a man named William Parker is building a network to fight back. When slave catchers come to his door, that resistance explodes into violence.

How did one law push the country dramatically closer to war? And what happens when the people targeted by this law refuse to surrender?