Set in the late 8th century, Senua is a Pict warrior from Orkney who embarks on a journey into Helheim, the Norse underworld, to rescue the soul of her dead lover Dillion from the goddess Hela. Carrying his severed head as a vessel for his soul, she must overcome trials, defeat mythological beings, and survive the influence of the Darkness, a malevolent entity that haunts her. Senua suffers from psychosis, hearing voices she calls "Furies" and experiencing hallucinations that blur the line between reality and delusion. Guided by memories of her friend Druth, a former slave of the Norsemen who taught her their legends, Senua pushes deeper into a hostile world shaped as much by her fractured mind as by the myths she believes in.