Louis IV was brought back from exile in England and set on the throne by Hugh the Great, the father of Hugh Capet. He was the next-to-last of the Carolingian Kings (Williamson, David. Debrett's kings and queens of Europe. Topsfield, Mass. : Salem House Publishers, 1988, pg. 67-68).
I cannot be certain whether or not Eadgifu, wife of Charles III, was the natural mother of Louis IV. Other descendants of Louis in Browning, Charles H. Americans of royal descent, 7th ed. Baltimore : Genealogical Pub. Co., 1986, pg. 362, 380.
aka Transmarinus. King of France.