Through a telescope, Robinson Crusoe, standing with his dog Dundee, spots a sloop heading toward shore. He's astonished when he sees an English flag on the stern. Excited by the notion of rescue, he jolts into action, running through the jungle, Dundee behind him. He "zip lines" to his tree house and sets off a pre-set series of fire signals on the island, then runs to the beach. Crusoe can't see they are a bunch of escaped pirates and yells at them. Their leader, Lynch, fires his gun. Crusoe sees they aren't English sailors, but pirates, and runs into the jungle.
Cook, Dover and Tibbetts go after Crusoe, who leads them through a set of booby traps. Crusoe triggers the first trap, killing Dover in a hail of arrows. Cook trips a wire and is strung up by his neck. Tibbetts, more wary, proceeds cautiously. He trips one of Crusoe's traps with a stick, narrowly escaping two beds of bamboo spikes that slam together. Crusoe hears and relaxes, but surprise, Tibbetts is alive. He shoots and misses Crusoe, who runs toward a native pointing a bow and arrow. He dives at his friend Friday's feet as he releases the arrow, hitting Tibbetts in the shoulder.
They ask Tibbetts who he is, but he's not talking. When Friday moves to pull the arrow out of his shoulder, Tibbetts talks. He says they have a map to Conquistador gold on the island. Lynch thought Crusoe would be after it. Crusoe learns they have no ship, just the small sloop they came ashore in. Friday still wants his arrow and pulls it out. Tibbetts advises Crusoe against sailing back with his cutthroat shipmates. Crusoe says they won't interfere, but asks that when he reaches the mainland to tell someone in authority where the island is and that a man wants to return to his home. Tibbetts agrees, saying no one has shown him respect in 20 years.
Lynch interrupts, leveling his pistol at Crusoe. Lynch wants Crusoe to read a map tattooed on the elderly Fenwick's back and lead them to the gold. When Crusoe says he can't help them, Lynch tells his crew to demonstrate what happens if he doesn't help. They move on Friday, but he jumps over the cliff to escape. "That wasn't really what I had in mind," Lynch says. Crusoe sees Friday peeking over and distracts them by reading the map. Friday escapes into the jungle. When Crusoe doesn't know the cryptic meaning of a poem on the map, Judy, the sole woman, slugs him hard. She knows he's lying and says there are worse things than being marooned if he doesn't help them.
Dundee tags along as Crusoe leads the group to the Kissing Rocks, mentioned on the map. He asks what happens to him after this. Lynch is vague, and Crusoe knows he can't trust him. Crusoe asks Judy about the map. She says her father, who was a thief and pirate, made it. She asks him about his father. Thinking back, Crusoe remembers a somber boat trip with his father, James Crusoe, who told him to be brave and "Draw strength from better times when an unhappy day comes along." His father's friend, Mr. Blackthorn, is waiting for them on shore, outside the riverside mortuary. Young Crusoe asks why he's here. His father says he fears he needs a friend today. Blackthorn takes his father inside.
On the island, Crusoe points out the highest peak. The pirates decide to rest. Crusoe makes his move and dashes into a cave. They give chase, and Judy cuts him off, holding her sword to his chest. Angry, she challenges him to a duel. He won't fight until she challenges him to knock her sword out of her hand. She's a formidable foe, and during the fight, Bagwell trips Crusoe and he falls. Judy, furious at Bagwell for helping, says, "Never help me." Laporte says Crusoe should thank Bagwell, as Judy would have killed him. Crusoe doesn't think so. Laporte says, "Gold or no gold. When you see that face on her... that's the face of death."
Crusoe flashes back to his boyhood in England. He walks through an underground morgue lined with bodies. Blackthorn explains they bring anyone who drowns in the river here. Paupers, orphans, suicides. Crusoe's father James lifts a shroud from one of the bodies and sees his wife, Alice. He cries, not understanding. "She told me she was happy," James sobs, as a blank-faced Blackthorn holds him.
At the tree house, Friday goes to his and Crusoe's arsenal. He grabs a pistol, machete, several knives and a bow and arrows. Armed and ready for action, he takes off after Crusoe.
To thwart further escape attempts, the pirates make Crusoe haul the powder kegs single-handedly. As they rest, Fenwick eats some red berries that Crusoe warns might not be safe. Fenwick says he spent 16 years in a Spanish prison and can eat anything. He recounts that in jail Judy's father tattooed a treasure map on his back using a rusty nail and soot.
Flashback as Young Crusoe sits on an above-ground tomb, staring at the stone on his mother's grave. Two young girls and a boy approach and try to get the "strange boy" to speak, as he hasn't since his mother died. Susanna introduces herself and says her mother died too. She reaches out to him. She's the girl he eventually marries. Fast forward to later in life, Crusoe as a young man carries Susanna through a London alley.
Crusoe asks Lynch if he's going to kill him once he finds the gold. He says he won't, but Crusoe doesn't believe him. They spot Eagle's Eye - a landmark from the map. Tibbetts is weak and suffering from his wound, so Lynch shoots him dead. Crusoe scans the landscape, and Judy asks him who he's looking for. He says a guardian angel, and she says there aren't any. Crusoe says, "That depends who is watching over you." He flashes back to when Friday was paddled ashore by cannibal warriors, tied to a wooden yoke and terrified.
The group comes to a river and makes Laporte walk out to the middle to see how deep it is. Something bites him, and then another thing bites him. They ask Crusoe what's in the river, but he's not telling. The man stabs a fish and brings it above water. It's a piranha. The swarm of fish attacks and he goes under. Lynch is angry, but Judy is impressed with Crusoe's cunning. Lynch threatens to cut off Crusoe's fingers, and Crusoe tells them the safe way across the river.
High up on a suspended treadmill, Fenwick crosses the river. At the resting spot, Friday finds Tibbetts and steals his coat, then continues to track the crew. At the cliff, Lynch tells Crusoe that Laporte had fancied Judy. He says the night before we lost the ship, Laporte whispered something to Judy. She held him down with one hand and almost took his eye out with the other. He says he wouldn't want to be the man who tames her.
Flashback to Crusoe with Susannah, showing her a loft area he's turned into living quarters. Everything in it is devised or improvised from odd materials, much like his tree house. A bed of covered hay bales. Dining chairs cut from barrels. A table made from an old door. Screen panels made from broadsheets and flour paste. She's impressed with his ingenuity and charmed, but it's clear Susannah wants real furniture in a real home. Susannah also tells him she's pregnant.
As Bagwell crosses the gorge, Friday fires at Lynch and misses. He fires again and narrowly misses Crusoe. Judy grabs Crusoe at sword point and commands him to throw his weapons over the cliff. He does. She then tells Friday to jump, but he doesn't.
Another group of marauders arrive, Captain Santana and five ramshackle Spanish guards. Santana sees the pirates' sloop and shoots a hole in it. A Spanish guard sneaks up on Friday, who knocks him out by knocking some coconuts loose from a tree. He carries the man to Santana's camp and tells them he can lead them to the pirates. Friday says the pirates are looking for gold. Santana says they have already scoured the island and that there is no gold.
Judy asks Crusoe how she and "his savage" Friday met. He says Friday is no savage, and flashes back to his arrival. Friday has been captured by cannibal warriors, who intend to sacrifice him. In the present, Lynch thinks Crusoe is leading them astray. He notes the sun's placement. Lynch wants to kill Crusoe, who challenges him to do it. Crusoe says they are in the middle of the Eagle Eye - another landmark on the map. He dares Lynch to shoot him and find the gold on his own. Lynch backs off.
Judy tells Crusoe that her father captured the gold on its way to Spain. His crew cast it in the shape of a cannon to smuggle it home, but were forced to bury it when they realized they would be caught, and swore never to reveal it. Crusoe flashes back to his days as a young man in London, when he explained to his father that it's important for him to make it on his own to prove to Susannah's father he isn't marrying her for money. His father says he can't raise a family on pride, and he'll speak to Blackthorn about a loan. Blackthorn offers him $1000, an astonishing amount. He offers it if Crusoe will let Blackthorn, a childless bachelor, let him be his godfather.
Back on the island, the crew comes to a waterfall. According to Friday, the pool at the end of the falls has no bottom. They ask Crusoe where the golden cannon is. He points behind them and they look. He then dives off the cliff. He's knocked unconscious, but Friday saves him. The Spanish fire on the pirates and take them prisoner. Friday excitedly tells Crusoe that they're leaving the island. However, Crusoe knows differently. He says they are the Spanish Guarda Costa, who hunt down and lock up English mariners. They're the last people he can surrender to.
Back at the tree house, Crusoe gets a drink from his "juicer." The pirates and Spanish, now in cahoots since there is gold involved, follow Dundee the dog back to the tree house. They see Friday and shoot at him. Crusoe activates a lever that sets in motion a set of pulleys and counter balances. Heavy panels of planks flip up from the tree house floor and cover the open sides. The tree house is now a fortress. Friday asks Crusoe why they're being attacked. Crusoe says it's because they think he knows where the gold is and in fact he does. He tells Friday that the tree house is on top of the gold.
The pirates set a fire to the trunk of the house to smoke Crusoe and Friday out. But the castaways have cleverly rigged explosives to the base of their water barrels in the tree house. They light the charges, and the sudden man-made deluge douses the flames around the base. Friday scrambles for the storage platform to retrieve some dry gun powder but can't reach it. Crusoe and Friday cleverly rig a series of makeshift weapons and take out two of the Spanish soldiers.
At night, Judy, clearly smitten with Crusoe, sneaks into his tree house and tries to convince him to give up. He refuses. She says pity, but she'll kill them quick if it comes to that. Below, Santana tells Lynch that he hasn't proven Crusoe can show them the gold. Santana says they aren't partners, and if they don't find the gold tomorrow they'll have to take them prisoners. Lynch protests, but Santana says he lost two soldiers and has to show their mothers that they lost their lives for something. Crusoe and Friday notice that their enemy has rigged a catapult and it is aimed at them.
Friday, terrified of being captured again and sacrificed, remembers the day he was rescued. In his flashback, he and another prisoner were rowed ashore by a hoard of frenzied cannibal warriors - a murderous band of his own people. Crusoe watches from a hidden vantage point as they kill the other prisoner. Just as they are about to slit Friday's throat, Crusoe fires on them and kills a few. Friday and Crusoe escape. Their first meeting. Friday is frightened as Crusoe tries to introduce himself.
The next day, under siege, Crusoe and Friday are bolted as a boulder hits the tree and shakes the tree house. The pirates and the Spanish launch a lit powder keg, but the fuse is too short and it explodes before it can reach its target. As their attackers load another keg, Crusoe and Friday scramble to find something to blow it up before it gets to them. Crusoe heats up a metal ramrod until it's glowing red. As the keg is launched, Crusoe shoots it with the red-hot rod, causing a huge explosion. The blast takes out the catapult and most of the men. The rest run off. Crusoe and Friday inspect the damage, including a crater from the explosion that has revealed the buried gold cannon.
Friday notices that not everyone is there. Realizing there might be spare boats, they run to the beach where Santana and a guard have taken Judy prisoner. She says they've given up on the gold, then breaks free and kisses Crusoe. Santana says he could kill them both, but it satisfies him more to leave him to rot on the island. The Spanish Galleon sails off, and Crusoe and Friday are again the only inhabitants of the island.
Friday asks about the gold and Crusoe says to bury it. It's cursed. Friday says that if that's so, burying it won't help. Instead, they drop the cannon over the side of the cliff and let the sea claim it. Crusoe wonders if he just threw away a fortune, although it was worthless to him on the island. Crusoe scans the ocean again with his telescope, longing for home and his loved ones.