Dr. Charles Gaudet, who has been convicted of treason for treating a wounded escaped convict, is sentenced to Devil's Island, where he is subjected to the cruelty of the sadistic commandant, Colonel Armand Lucien and is condemned to hard labor. During an attempted escape by the convicts, Lucien's little daughter Collette suffers a fractured skull, and only Gaudet, a skilled brain surgeon, can save her life. The doctor has been condemned to death for his role in the escape, and consequently, Lucien offers Gaudet his life for that of Collette. Gaudet agrees to Lucien's terms, but after saving the little girl's life, the doctor is ordered to the pit by Lucien. This angers Madame Lucien, who in gratitude for her little girl's life, plots the doctor's escape. With bribes provided by Madame Lucien, Gaudet and his compatriots escape the island aboard a small boat. When the craft runs out of fuel, however, the fugitives are picked up by a convict ship and returned to the island, where Lucien sentences Gaudet to death. Learning of the doctor's fate, Madame Lucien hurries to the mainland and pleads for Gaudet's life with the newly appointed minister of the penal colonies. Having discovered Lucien's reign of graft and corruption, the minister returns to the island with Madame Gaudet where, after pardoning Gaudet, he arrests Lucien for misconduct and promises to institute reforms.