This paper revisits intervention effects in Mandarin Chinese why-questions. I present a novel empirical generalization, in which it is shown that the ability for quantifiers to induce intervention hinges upon their monotonicity and their ability to be interpreted as topics. I then propose a semantic account of intervention that correlates topicality with the monotone properties of intervening operators. A crucial assumption in this account is that why-questions in Chinese are idiosyncratic, in that the Chinese equivalent of why directly merges at (...) a high scope position that stays above a propositional argument. Combining the semantic idiosyncrasies of why-questions with the theory of topicality, I conclude that a wide range of intervention phenomena can be explained in terms of interpretation failure. (shrink)