Hidden Agenda follows homicide detective Becky Marney and district attorney Felicity Graves as they investigate doubts about a convicted serial killer's guilt. Five years after the Trapper killer's arrest, Finn awaits execution while maintaining his innocence, prompting both women to reexamine the case. Players shape the narrative through a companion smartphone app that connects to the PS4, making choices that affect character relationships, uncover evidence, and determine the true identity of the killer. The game features both single-player story mode and competitive multiplayer, where participants pursue hidden objectives. Through quick-time events, clue searches, and dialogue choices tracked via the app's logbook system, players navigate three chapters of branching storylines that can lead to multiple conclusions, including the possibility of becoming a suspect themselves.