Disclaimer: Not my sandbox.
Something's worrying him. She can tell, mostly because he hasn't made any inappropriate comments towards any of her nurses yet today, which is a rare miracle for which she is very thankful. In a way. In the way that at least she won't have to pretend to hate him today. But, if she were to be completely honest with herself- it's killing her. He's always cheerful, well, not cheerful, but never this melancholy.
He smiles when no one else can even bear to use that many facial muscles. He sings (badly) when everyone else is finding breathing too tiring for their liking. Somehow, his refusal to cave in inspires the rest of them- a long time ago, it seems, Henry Blake said that he was the heart of the camp- she'd thought Henry insane at the time (and still thinks that he was off his rocker) but now she knows he was right. He's the heartbeat of the camp.
And he's her heart, which, watching him while he stirs his coffee listlessly and looks inches from tears, has stopped beating entirely, she thinks.