The Uruk-hai capture Frodo and Sam at Amon Hen, thus Saruman gains possession of the most powerful of the Rings of Power, which carries in it, a greater part of Sauron's inherent might.
But what does Saruman do now?
Does he use his great voice, enhanced by the One to subjugate the free peoples of Middle-earth?
Does he take command of the combined forces of the enemy in Sauron's place?
Does he go into hiding to study the One, knowing he cannot wield it to its full potential, and try to replicate it and create his own ruling Ring?
Does he enslave Sauron, thus making him the 10th Nazgul?
Does Sauron assail Orthanc in an attempt to regain the One?
And what of the free peoples of Middle-earth? Now faced with the potential of two foes waging war on each other, do they come together and strike both Sauron and Saruman while they're occupied fighting for possession of the One?
Some notes from Tolkien as to what would happen if others gained possession of the One Ring:
From Letter #246
But what does Saruman do now?
Does he use his great voice, enhanced by the One to subjugate the free peoples of Middle-earth?
Does he take command of the combined forces of the enemy in Sauron's place?
Does he go into hiding to study the One, knowing he cannot wield it to its full potential, and try to replicate it and create his own ruling Ring?
Does he enslave Sauron, thus making him the 10th Nazgul?
Does Sauron assail Orthanc in an attempt to regain the One?
And what of the free peoples of Middle-earth? Now faced with the potential of two foes waging war on each other, do they come together and strike both Sauron and Saruman while they're occupied fighting for possession of the One?
Some notes from Tolkien as to what would happen if others gained possession of the One Ring:
"It was part of the essential deceit of the Ring to fill minds with imaginations of supreme power. But this the Great had well considered and had rejected, as seen in Elrond's words at the Council. Galadriel's rejection of the temptation was founded upon previous thought and resolve. In any case Elrond or Galadriel would have proceeded in the policy now adopted by Sauron: they would have built up an empire with great and absolutely subservient generals and armies and engines of war, until they could challenge Sauron and destroy him by force. Confrontation of Sauron alone, unaided, self to self was not contemplated. One can imagine the scene in which Gandalf, say, was placed in such a position. It would be a delicate balance. On one side the true allegiance of the Ring to Sauron; on the other superior strength because Sauron was not actually in possession, and perhaps also because he was weakened by long corruption and expenditure of will in dominating inferiors. If Gandalf proved the victor, the result would have been for Sauron the same as the destruction of the Ring; for him it would have been destroyed, taken from him for ever. But the Ring and all its works would have endured. It would have been the master in the end."
"Gandalf as Ring-Lord would have been far worse than Sauron. He would have remained 'righteous', but self-righteous. He would have continued to rule and order things for 'good', and the benefit of his subjects according to his wisdom (which was and would have remained great)."
"Thus while Sauron manipulated [illegible word] evil, he left "good" clearly distinguishable from it. Gandalf would have made good detestable and seem evil."
From Letter #246