Script Entertainment (SE), originating from murder mystery games, has flourished in China over the past decade. Beyond entertainment, it has gradually evolved into a brand new game genre and a vast industry integrating with education, cultural tourism, commerce and so forth. Against this background, extended reality (XR) has become a key driver for the digital transformation of SE industry. However, the current use of XR technology in SE remains simply enhancing visual and audio effects, with limited interactability and integration into game mechanics. In this Research-through-Design (RtD) study, we explored what aspects and how XR can mediate SE. First, we conducted expert interviews with 10 SE practitioners to gain industrial perspective and initial design insights. Second, we developed an annotated portfolio that comprises a set of game demos co-created with SE industry stakeholders and game creators. As a result, 4 actionable design implications were generated. Grounded in both our designerly practices and industry perspectives, we intend to contribute fresh and in-depth insights for future design and development of XR-mediated SE.