The Regent (released Voltaire) P (having discovered that he had imprisoned) Q (Ran innocent man and gave him a pension) S The correct sequence should be

Since, the starting statement carries a subject; the next statement will carry a verb i.e. Q follows as it mentioned the discovery of the Regent. R will bethe continuing statement which states what he actually discovered. P follows next as it talked about the reaction of the Regent after the discovery. And S would be the concluding statement and thus form a coherent paragraph.

The correct formation would be, ‘The Regent having discovered that he had imprisoned an innocent man released Voltaire and gave him a pension.’