Ok, so here is the scenario.
1 out, runners at first and third.
batter hits a fly ball to shallow right field. Runner at first base does not tag up and takes off. Runner at third base waits. Right field makes a diving catch, runner at third tags up and crosses home plate before right field throws to first base to get that runner out.
Would the 3rd out be a force since he did not tag up, thereby eliminating the run scored?