One of the challenges in designing an interactive cinematic experience is to offer interactive choices, which does not distract the user from immersion into the story. The interactive film Lost Cause focuses on the life of the main character explored through the perspectives of three characters. The correlated design of interface, interactions and narrative structure in Lost Cause uses different techniques to support an immersive yet engaging interactive story experience. One technique is to build an interface which encourages smooth viewer oscillation between the content of the story and interactivity of the interface. Another technique is challenged-based immersion created through viewer's navigation to discover the story. A user study was conducted to analyze how well interactions in Lost Cause affect viewer understanding and immersion into the story. The results from this study suggest the overall design is versatile and provides various degrees of viewer immersion.