Sentence:  His work can mainly be divided into classical adaptations, usually with a dark heart, and apparently fluffy country-house comedies, often concerned with aristocrats and actresses, though these also tend to be <WSD>dark-hearted</WSD> and fundamentally, if not tragic, then at least elegantly sad about the human condition and its various compromises and betrayals. 
Meaning of the word marked with <WSD> tags:  Bleak.