In 1840, seven years after the beginning of the Seminole Indian war in Florida, U.S. Army General Zachary Taylor sends for naval officer Lieutenant Richard Tufts to undertake a special mission to defeat the Indians. Upon his arrival in Florida, Tufts meets his scout, Monk, who guides him through the alligator-ridden swamp to the island home of the mission's commander, Capt. Quincy Wyatt, a reclusive widower and an expert swamp fighter. After bidding farewell to his five-year-old son, whose mother was a Creek princess, Wyatt goes with Tufts and Monk to Army headquarters, where they receive their official instructions from General Taylor and inspect their troops. Wyatt and his company then pursue the first objectives of their mission--to recapture a western fortress taken by the Seminoles and free the white prisoners being held captive there. No sooner do Wyatt and his men free the prisoners, among whom is the beautiful Judy Beckett, than they are pursued by the Seminoles and forced to abandon their plans to board a rescue boat on Lake Okeechobee. Wyatt commands his forces to beat a hasty retreat deep into the Everglades, where a brush fire is set to hold back the approaching Indians. The fire keeps the Indians temporarily at bay, but things look bad for Wyatt when the drumbeat of the Indian battle cry is sounded and the platoon is faced with little room for escape. Thinking quickly, Wyatt decides to send his platoon with Sgt. Shane, while he and Tufts stay behind to build canoes, which will be used to rendezvous with the platoon at the Indian burial grounds. During this time, a romance is sparked between Wyatt and Judy, who tells Wyatt that she is intent on returning to Savannah to take revenge upon the man who killed her father. When the canoes are completed, Wyatt, Tufts and Judy journey to the burial grounds, but Shane and the platoon are not there when they arrive. They decide to wait, but the only person who emerges from the darkness is Monk, who arrives with news that the platoon has been ambushed and massacred by the Seminoles. Meanwhile, General Taylor, fearing that Wyatt's platoon has met its demise in the Florida swamps, calls off his search for the fighters and orders his men to rescue Wyatt's son. When Wyatt and the others finally make it to Wyatt's island, they find it burned out and the boy missing. Fearing that his son is dead, Wyatt decides to end his retreat and fight his attackers. After he defeats Chief Ocala, the Seminole chief, in a daring underwater fight, the rest of the Seminole warriors capitulate and flee in fear. Wyatt's success is made sweeter when General Taylor safely delivers his son and Judy decides to stay with him on the island.