You play the agent of the organisation that never existed, which has a clear view of how the history of the universe must play out. To make sure that the timeline flows as they want to, they send you to specific space-time locations, STLs, where you are left alone with the task to make sure events play out as they want to. You must first observe the current state of the STL, in order to be able to make a clean cut in the timeline to alter the flow of events. Even though your missions are placed in a deterministic univerese, the chaotic behaviour of 'the Butterfly Effect', is your prime enemy. You must make sure your actions don't have uncontrolled consequences and contaminate the timeline more than what is absolutely necessary. You are the weapon that can rewrite history...