Prince Kassim (Damien Thomas) is about to be crowned Caliph of Charak, but his evil stepmother Zenobia (Margaret Whiting) puts a curse on him, turning him into a baboon. Sinbad, Prince of Baghdad (Patrick Wayne), sails into Charak to ask leave to marry Kassim’s sister Princess Farah (Jane Seymour) but finds the city under curfew. Sinbad and his men are offered dinner by Rafi (Kurt Christian), but one of the men is poisoned and they are attacked by Rafi, who is Zenobia’s son. Sinbad defeats him, but Zenobia summons up three ghouls, which he also defeats.

Sinbad meets with Farah, who knows that Kassim’s curse is a spell cast by Zenobia. If he is not cured in seven moons, Rafi will become Caliph. Sinbad, Farah, and his crew set off to seek the old Greek alchemist Melanthius (Patrick Troughton) on the Isle of Casgar, who they believe can break the curse. They bring along Kassim in a cage, slowly becoming more baboon-like.

Zenobia and Rafi follow in a ship propelled tirelessly by the Minoton, a bronze automaton in the form of a Minotaur. Sinbad and Farah land at Casgar and find Melanthius and his daughter Dione (Taryn Power), who wish to help them. But they must travel to Hyperborea. On the way, Kassim begins to fall in love with Dione.

Zenobia transforms into a seagull to fly to Sinbad’s ship and then into a tiny human to listen to Melanthius explain the cure. Kassim spies her and Melanthius and Sinbad capture her, but her potion spills, a wasp drinks it and grows to enormous size. Sinbad kills it, but Zenobia transforms into a seagull again to escape. When she turns back to human, her foot remains a seagull’s foot.

Sinbad’s ship reaches the polar wastelands, where they are confronted by an eight-foot caveman with a horn, a creature called a Troglodyte, which proves friendly. Trog leads them to a giant pyramid called Shrine of the Arimaspi. Zenobia arrives first and the Minoton removes a block of stone to enter, which crushes him and weakens the pyramid and its power.

Sinbad and team arrive and enter the shrine, frozen and guarded by a Smilodon, a sabre-toothed cat who is guardian of the shrine. Zenobia orders Rafi to attack Melanthius and Dione, but Rafi is attacked and killed by Kassim. Kassim is restored to human form and Zenobia transforms into the cat, which attacks Sinbad’s party. The Troglodyte attacks the Smilodon. Trog is killed, but Sinbad kills the cat and Zenobia with a spear. They all flee as the temple collapses. They return home and Kassim is crowned Caliph.

Sam Wanamaker directed the dramatic portions of the film, Charles Schneer and Ray Harryhausen the technical parts. Peter Mayhew (Chewbacca) portrayed the Minoton in some scenes, his first movie role, though Star Wars was released first. Patrick Troughton is the second Doctor Who. Jane Seymour is of course Solitaire in Live and Let Die, Serina in Battlestar Galactica, not to mention roles in Amadeus, Somewhere in Time, and countless other roles in movies and TV. The giant doors of the Arimassi Shrine were inspired by the doors in the original King Kong, and the interior of the shrine by one in She. The Troglodyte re-appeared as Calibos in Clash of the Titans. Jane Seymour had a semi-nude scene, believe it or not.

Sadly, the film was released just after Star Wars, and few paid any attention. The animation took Harryhausen one and a half years to do. The special effects received some unfavorable reviews, except for the baboon, which many people thought real, and the Smilodon/Troglodyte battle. The Minoton is a Minotaur Automaton. It was Ray Harryhausen’s second costliest film, outdone by Clash of the Titans. Taryn Power is the granddaughter of Tyrone Power and Patrick Wayne the son of John Wayne. Originally, John Phillip Law of the Golden Voyage of Sinbad was supposed to reprise his role here.