This one is terribly short, but I like the idea and might expand on it sometime. Give me your thoughts about it.
He is not concerned when she arrives home drenched in sweat; Vulcan is hard planet for a human to become accustomed to.
He is not worried when she stumbles wearily in the hallways, for she constantly tells him that the heat simply makes her drowsy.
He becomes mildly anxious when she slumps against the wall, her eyes fluttering closed.
He becomes terrified when she collapses on the floor, her temperature ablaze and completely unresponsive.