In "Boundless," Detective Carl Mørck and his team from Department Q revisit a chilling cold case set on Bornholm Island, Denmark. The case involves the mysterious death of a young girl, intertwined with the activities of a local cult and a string of disappearances of young women. As Mørck delves deeper into the investigation, he must not only solve the perplexing case but also confront his own dark past to pave the way for a new life with his fiancée. However, the island's ominous secrets and dangers threaten to engulf them all as they unravel the truth behind the girl's death and the sinister forces at play.