At the turn of the century, Nathan Walker comes to New York City to take the most dangerous job in the country. A sandhog, he burrows beneath the East River, digging the tunnel that will carry trains from Brooklyn to Manhattan. In the bowels of the riverbed, the sandhogs — black, white, Irish, Italian — dig together, the darkness erasing all differences. Above ground, though, the men keep their distance until a spectacular accident welds a bond between Walker and his fellow sandhogs that will both bless and curse three generations.