Mary, a beautiful half-caste girl raised with the natives of a South Sea island, gradually arouses the passion of beachcomber Dan McGuire, a derelict and a drunkard. One day, Walter Kincaid, the consumptive nephew of the island's missionary, comes to the island mission in search of his health. Walter is attracted to Mary, who uses his infatuation to inflame Dan's jealousy. Walter's sudden collapse brings both Mary and Dan to his bedside, and the two nonbelievers are so deeply moved by Walter's Christian spirit that Mary throws her wooden idol into the sea while Dan renounces alcohol. One day, while all of the island's male inhabitants except Walter are away on a fishing trip, a band of slave traders attacks the village, and Walter beats the war drum, alerting the islanders. Dan and the others rush back to the village and, after rescuing the women, find Walter in the throes of death, having been felled by the slavers after a fierce hand-to-hand battle. His death sanctifies Dan and Mary's love, and they are united in a Christian marriage.