Heartless Frost, Dr. Z's Awakening

Dr. Rowan Lawson spent a decade crafting a miracle cure for Dawn Summers, only to watch her gift the triumph — and her heart — to another man. When her new lover deliberately destroyed the serum to force him out, and Dawn stood by in silent approval, Rowan's devotion finally froze over. He vanished from her world and returned as the medical world's most formidable and elusive legend: Dr. Z.