Heartless Frost, Dr. Z's Awakening

Rowan Lawson has wanted Dawn Summers for ten years, and for those ten years he has been working on a medicine for her heart. The medicine is the only thing that can keep her alive. When the serum is finished she hands the credit for it to a man she used to love, who has come back into her life, and she goes to him as well. This man shuts off the heating for the whole building in the middle of winter so that Rowan will have to leave. The only dose of the serum in existence starts to break down in the cold. Rowan does what he can to stop it and is told he is being petty and jealous. Dawn stands and watches without saying a word. That is the point where his feeling for her stops. He tells her that from now on whether she lives or dies has nothing to do with him, and he leaves. Some time later he comes back under another name, Dr. Z, a doctor the medical world knows by reputation and almost nobody has met in person.