Tom is a quiet, scarred World War I hero who seeks refuge as the lighthouse keeper on the remote Janus Rock. He finds comfort in the straightforward rules of his post and the deep isolation of the island. Estranged from his surviving family, he is a stoic man whose strong moral compass is tested when a life-altering choice washes up on the island's shores.

Isabel is a bold, fearless young woman from Point Partageuse who marries Tom and joins him on Janus Rock. Having lost her brothers to the war, she is fiercely determined to build a family and refuses to be a passive victim of fate. She drives the central conflict when she convinces Tom to keep a shipwrecked infant as their own.

Hannah is a local woman from a wealthy family who becomes estranged from her father after marrying an Austrian man following the war. She is haunted by the sudden disappearance of her husband and infant daughter. She refuses to give up hope of finding them, despite the town's belief that her grief has driven her mad.

Frank is Hannah's Austrian husband who endures strong anti-German prejudice in post-war Australia. Known for his enduring patience and capacity for forgiveness, he flees a drunken mob with his infant daughter in a dinghy, hoping to wait out the danger on the water.

Septimus is a wealthy, self-made timber man and Hannah's father. Originally an orphan, his hardworking and frugal nature makes him a revered citizen in Partageuse. He disowns Hannah for marrying Frank but attempts to offer support and reward money after tragedy strikes her new family.

Lucy is an infant who miraculously survives a perilous journey at sea, washing ashore on the remote Janus Rock. She becomes the center of a profound moral dilemma for the island's isolated inhabitants, bringing both immense joy and heavy consequence to the lighthouse keeper and his wife.

Gwen is Hannah's sister and Septimus's daughter. She is a supportive presence in her sister's life, attempting to manage the complex emotional fallout of their family's tragedy while acting in what she believes are the best interests of her loved ones.

Violet is Isabel’s mother, who carries the deep, unending pain of losing two sons to the war. Her grief shapes her family's dynamics and heightens her overwhelming joy when she believes she has been blessed with a new grandchild.

Bill is Isabel's father and Violet's husband. Like his wife, he has suffered the devastating loss of his sons in the war, a tragedy that makes him fiercely protective of his surviving daughter and desperate for any source of familial happiness.

Ralph is a crew member on the store boat that visits Janus Rock every three months. He represents a rare link to the mainland for the isolated lighthouse keeper. He offers pragmatic advice and friendship rooted in the shared grief of their post-war community.

Bluey is a younger crewman on the store boat. Observant and well-meaning, he is friendly with Tom and Isabel but finds himself caught in a moral predicament when he notices a distinctive object that links the island to a mainland mystery.

Sergeant Knuckey is a local police officer in Partageuse who is intimately connected to the community's tragedies. Having lost a son himself, he brings empathy and a measured, patient approach to law enforcement.

Sergeant Spragg is a harsh and aggressive police officer from outside the close-knit community of Partageuse. Unsympathetic to the grief that binds the locals, he brings a cynical, hard-line approach to his police work and is quick to judge the town's residents.

Trimble is the former lighthouse keeper whose post Tom temporarily fills. Driven mad by the isolation of Janus Rock and the grief of losing his beloved wife, his tragic fate serves as a grim warning about the psychological toll of the island.

Neville is a retired lighthouse keeper who briefly steps in to maintain the light following Trimble Docherty's breakdown. He helps orient Tom to the duties of the post and represents the institutional continuity of the lighthouse service.

Cecil is Tom's older brother. Growing up under an abusive father, Cecil often deflected punishment onto Tom, leading to a profound estrangement between the brothers in their adult lives.

Hilda is Ralph's wife, a resident of Partageuse who is well-versed in the local lore and history. She serves as a source of information about the mainland's ongoing grief and the unresolved mysteries surrounding the Roennfeldt family.

Hugh is one of Isabel’s two brothers who were killed in the war. His death deeply traumatizes the Graysmark family, leaving them desperate for a reason to feel joy again.

Archie is Isabel’s other brother who lost his life in the war. The permanent absence of the brothers leaves a heavy void in the lives of his parents and sister.

Moira is the beloved deceased wife of Trimble Docherty. Her untimely death destroys her husband's sanity and serves as a haunting reminder of the harsh, unforgiving conditions on the island.