Beth looks for her cousin Patrick at Whit’s End. She finds him in the Imagination Station. He is upset because his mom is making him go to a birthday party at Grandma’s, which means he has to miss a soccer game. Beth tries to comfort Patrick, saying she’ll be at the party, too, and offers to sit next to him. In his foul mood, he doesn’t think that will make a difference. Beth’s feelings are hurt.
Patrick messes with some of the buttons in the Imagination Station, and it turns on. Although they are not allowed to use the machine without permission, Patrick starts it anyway and an adventure begins.
The cousins find themselves on an ocean ship. They hear an announcement that cannibals are coming via canoes. When they meet a man with a peg leg, they fear that he is a pirate. Instead, he’s the surgeon’s mate, Newland Nettleton, a sailor in the British Navy. He accuses the children of being stowaways and takes them to the captain of the ship, Captain Home.
When the children meet Captain Home, a missionary named Calvert is asking him if he can go ashore to the island. Home refuses, saying that it’s too dangerous and that Calvert will die; Calvert says that he died a long time ago so he could live for Christ. It is unclear how Calvert ended up on the ship, but it is implied that Calvert may have booked a passage to Fiji. The captain orders Nettleton to throw the stowaways in the brig, but Calvert convinces Capitan Home to leave Beth with him.
As Nettleton takes Patrick toward the brig, the criminals aboard the ship attempt to escape. At the same time, Toki, the king of the cannibals, addresses Captain Home from his canoe. Toki asks to come aboard the ship so he can trade for rifles, which the captain refuses, so Toki remains in his canoe as they talk.
Calvert asks the captain if he can go ashore, and Home once again refuses. Toki brags about burning villages of Christian Fijians and says that he hates God. The Christian Fijians are peaceful natives of the island and live apart from the cannibals.
Calvert warns Toki not to mock God. The captain wishes to never see Toki again, and Calvert says God loves the cannibals, even if others don’t. The cannibals leave.
The convicts try to take Patrick and Nettleton hostage and escape in a landing boat. As Nettleton attempts to stop the prisoners, Nettleton and Patrick are knocked overboard, along with the landing boat. They are swept away with it as a storm brews.
Calvert explains that he as been teaching Fijians and some of the cannibals the Bible and the English language. He says that he gave up his life to become a Christian, so it’s OK if he dies while fulfilling God’s calling on his life. He joins one of the boats trying to rescue Nettleton and Patrick.
Nettleton and Patrick are on top of the overturned landing boat. Nettleton resuscitates Patrick after he almost drowns. They struggle to stay on the boat as a whale shark makes a big wave. Nettleton explains that he lost his leg in an accident, and the captain kindly let him work on the ship.
Beth hides in one of the rescue boats as it pursues Nettleton and Patrick. The storm is suddenly upon them. Calvert discovers Beth, but they are too far to return her to the ship. Patrick and Nettleton eventually land on the island. The rescue party realizes that the cannibals that met with the captain have been swept into the sea by the storm.
Patrick and Nettleton create shelter out of one of the cannibals’ destroyed vessels. The rescue party arrives on another part of the island. A soldier who is a part of the rescue party, Sergeant Dunn, threatens to shoot locals and fires a shot. The Fijians claim to be peaceful Christians, and Calvert vouches for them. They tell the party that Toki is hunting for Patrick and Nettleton.
The storm ends. Patrick and Nettleton find supplies in a canoe. These supplies include turtle shells, and Nettleton tells Patrick that turtle shells are sacred to the cannibals. Toki tries to kidnap Patrick, and Nettleton tries to defend him. When Patrick threatens to break a sacred turtle shell, Toki backs off. The shells are a sign of the cannibal king’s power. If Patrick breaks a shell, he breaks Toki.
Patrick tells Toki that caring more about turtle shells than about people is backward. Toki says that Patrick talks like Calvert and that he hates God’s teachings. Patrick says that Toki is not much of a king if he needs a turtle shell for power. Toki seems fearful. He believes God took his tribesmen in the storm and that God will take him next. Nettleton tells Toki to give up his cannibal ways, and Patrick says that God will forgive Toki if he lets Him. Toki asks for a drum to send a message to the others on the island, but his motives are unclear.
Beth, Calvert and the rest of the search party hear the drums. Calvert translates that two people have been found and that Toki wants the Christians to come for Patrick and Nettleton. The rescue team heads toward the drums on a rescue boat. The Fijians suspect that Toki is using Patrick and Nettleton as bait. Calvert points out that Toki has broken every treaty he ever made and has no respect for human life. Sergeant Dunn hopes that Toki will fight so he can shoot him, but Calvert says not to hope for bloodshed.
Nettleton makes a fire with a lot of smoke in order to attract attention. Toki had left to send the drum signal, and Patrick doesn’t trust him. When the rescue boat approaches, Toki appears with a spear because the sailors have rifles. Toki guides them toward the rescue party.
As the rescue boat approaches, the smoke makes it hard for the sailors to see exactly what’s happening. Nettleton’s peg leg gets caught in the sand, so Patrick and Nettleton trip over each other and fall; the sailors see Toki standing over Patrick and Nettleton with a spear and mistakenly think he’s hostile. The rescue boat hits a reef, and Beth falls into the water. Beth struggles to swim in the strong current. Toki throws his spear at Beth and Sergeant Dunn shoots and wounds Toki.
The company from the ship discovers that Toki’s spear saved Beth from an angry stingray. Toki is badly injured. Nettleton, the surgeon’s mate, takes the bullet out of Toki with Patrick’s knife. After Nettleton takes out the bullet, Toki asks Calvert to tell God to spare him. Calvert prays, asking God to heal Toki and to bring his heart to repentance. Toki promises to stop killing Christians if he lives and repents, asking the Fijians to forgive him. The sailors begin to take Toki to the ship to stitch up his wounds. Nettleton and Calvert say their goodbyes to Patrick and Beth, who return to the workshop in the Imagination Station.
Patrick apologizes to Whit for using the Imagination Station without his permission. Whit tells the kids about the history of John Calvert, the missionary. He was an example of how Jesus calls us to pray for our enemies and give freely to others.
Patrick apologizes to Beth for being rude to her. He points out that even though he was rude to her, she came with the ship’s rescue party to save him. Whit invites the kids to get some ice cream, and Patrick tells Beth that he would enjoy the party if she went to their grandma’s with him.