Frank Gunn operates as a detective in the Special Crime Services (SCS), an elite unit tackling high-tech and organized crime. He is thrust into action when a violent assault, orchestrated by an assailant presumed dead, targets the SCS headquarters. This attack unveils the existence of supernatural masks granting users enhanced abilities, triggering a major SCS investigation into their origin, distribution, and criminal exploitation.

Within the SCS team, Gunn partners closely with colleagues James Blood, Sarah Sinclair, and Harry Creighton on complex cases entangled with the masks and related criminal conspiracies. His investigative efforts prove crucial in uncovering links between the masks, pharmaceutical entities like Echo Pharmaceuticals, and militant factions employing the masks for violent ends. His documented role within the SCS framework centers on evidence collection, suspect apprehension, and bolstering the unit's response to threats amplified by the masks' powers.

Gunn's active involvement spans the initial phases of the mask investigations and the pursuit of the associated criminal network. His documented role within the narrative concludes with the events of the first season.