"Johnny" (John Wayne) and his long-suffering partner "Pop" (James Gleason) do contract mining work and are building a tunnel for railway owner "Alexander" (Sir Cedric Hardwicke). This latter man is a bit of a pile driver and they are already arguing about safety and cost cutting at the tunnel when "Johnny" encounters his boss's daughter "Maura" (Laraine Day). Dad disapproves profoundly, but the two embark on a romance that leaves both estranged from her father - and that makes their digging even more dangerous. Can they reconcile their differences before disaster strikes? The last half hour pic...