Designing interactive technology to support safety-critical systems poses multiple challenges with respect to security, access to operators and the proprietary nature of the data. We conducted a two-year participatory design project with French power grid operators to both understand their specific needs and to collaborate on the design of a novel collaborative tool called StoryLines. Our primary objective was to capture detailed, in-context data about operators’ work practices as part of a larger project designed to provide bi-directional assistance between an intelligent agent and human operator. We targeted handovers between shifts to take advantage of the operators’ existing practice of articulating the current status of the grid and expected future events. We use information that would otherwise be lost to gather valuable information about the perator’s decision rationale and decision-making patterns.This paper describes how we combined a bottom-up participatory design approach with a top-down generative theory approach to design StoryLines, an interactive timeline that helps operators collect information from diverse tools, record reminders and share relevant information with the next shift’s operator.We conclude with a discussion of the challenges of working with users in safety-critical environments and directions for future research.