Shadow Of A Demon — E. Rose Sabin

"You must learn to communicate with him, to understand him," the Mother Superior of the Daughters of Mercy says of the thing that dwells inside India Terrano, the thing India regards as a demon. It is a Viseg, a creature that feeds on energy and can spit that energy out with tremendous destructive force. It has endangered India's family and blasted her fiance's mind, leaving him a living corpse. It has made her a fugitive, hunted both by the Solarian Patrol, which intends to put her to death, and by representatives of an interplanetary corporation, which wants to experiment on her to learn to harness the Viseg's power. To India the Viseg is a hated thing, a curse. She cannot possibly follow Mother Lira's advice. Yet how else can she survive and safeguard those she loves? But the path to communication and understanding will be fraught with many dangers, will bring pain and grief to her family and friends, and will lead her far from the only home she's known.