At the turn of the twentieth century, Nathan Walker comes to New York City to take the most dangerous job in the country: digging the tunnel far beneath the Hudson that will carry trains from Brooklyn to Manhattan. In the bowels of the riverbed, the workers - black, white, Irish and Italian - dig together, the darkness erasing all differences. But above ground, the men keep their distance until a dramatic accident on a bitter winter’s day welds a bond between Walker and his fellow workers that will both bless and curse three generations. Almost ninety years later, Treefrog stumbles on the same tunnels and sets about creating a home amongst the drug addicts, alcoholics, prostitutes and petty criminals that comprise the forgotten homeless community.