Whilst Sinbad (Kerwin Mathews) is on his way to Baghdad, transporting the Princess Parisa (Kathryn Grant), who is to become his bride and secure peace between her kingdom and his, the ship encounters the isle of Colossa. Sinbad and his men are attacked by a gigantic, bestial one-eyed Cyclops, and are saved only when the mysterious magician Sokurah (Torin Thatcher) appears and uses a magic lamp to protect Sinbad's men. But in the process of escaping harm, Sokurah loses the lamp to the Cyclops. He desperately wants to retrieve it and tries to persuade Sinbad to put about and return to Colossa — but the captain won't jeopardize the safety of the princess or the success of his mission, and the Caliph of Baghdad (Alec Mango) feels the same way, even after Sokurah amazes the court by conjuring up a snake-woman. It is only when the princess is shrunk by an evil spell, the breaking of which requires the shell from the egg of the giant Roc — which resides on Colossa — that Sokurah can get his expedition mounted, with Sinbad in command. With a crew made up of a handful of his bravest men and some of the most desperate convicts in the Caliph's prison, he has to contend with potential mutiny at every turn, and the men are driven almost to madness before they even reach Colossa. Once there, they find terrors as great as the Cyclops and the treachery of the magician, but Parisa — in her tiny state — also discovers the beautiful world inside the lamp, and the lonely boy genie (Richard Eyer) who inhabits it. They strike the bargain that, when Sinbad's bravery is added to the equation, will bring their quest to an end. If, that is, they can all survive the dangers that Sokurah puts in their path.