This paper examines two emerging discourse uses, topic-shifting and trail-off, of a temporal conjunction ranhou in spontaneous Mandarin conversation. Unlike traditional approaches that focus exclusively on such textual functions as temporality and consequentiality of ranhou, the present study considers the role of prosody in making ranhou recognizable as a topic-shifting and trail-off marker in interaction. Using the framework of conversation analysis, this paper reveals that, as a topic-shifting marker, ranhou signals both stepwise and disjunctive topic shifts; as a trail-off marker, it marks the closure of the current turn and invites the recipient’s response. The prosodic analysis demonstrates that the topic-shifting ranhou shows a significantly longer duration and larger pitch range than its other uses; the trail-off ranhou features intonational independence, loudness diminuendo, and/or durational lengthening. These prosodic designs, in collaboration with particular sequential environment, make the new discourse uses and their associated interactional purposes recognizable by conversation co-participants.