A small, ordinary moment turns into a quiet confession. The speaker touches a woman's hands and remarks that they are cold, the kind of thing anyone might say. Her reply is gentle but cutting: he hasn't touched her heart. She takes his comment about her body's temperature and answers it in terms of feeling, pointing out that he has noticed the surface and missed what really matters.
The speaker barely says anything, and the poem gives us only his short, almost clumsy observation. That brevity makes her line land harder. The word "darling" is interesting, because it could sound affectionate, sad, or a little teasing. Judging by the lowercase, unpunctuated way her words are set down, she may be speaking softly, without anger.
The mood is wistful and slightly chilly, like the hands themselves. There is disappointment here, and perhaps a hint that the speaker, and maybe the reader, has just realised the distance between them.