Stronghold - Stanley Ellin

Four desperate ex-cons attempt an audacious kidnapping
James Flood and his three partners get out of jail with a single number on their minds: $1 million, in cash, for each of them. To get it, they have a simple plan, a mixture of home invasion and kidnapping, with a brilliant twist: Their target is a wealthy family whose religion means they can't possibly fight back.

Armed with enough guns and ammunition to take on an army, Flood and his men storm the house of Marcus Hayworth, the leader of a small Quaker community in upstate New York. Though the police advise Hayworth to pay whatever it takes to set his family free, he plans to retaliate using nonviolent methods. But his commitment to pacifism slips just a bit with every minute that his family remains in the sights of James Flood's gun.