Magnum and Higgins are shocked when one of her former MI6 teammates shows up with a fresh gunshot wound and news that "the Viper," the assassin who killed Higgins' true love, has surfaced on Oahu. Also, while Magnum's busy helping Higgins track down the Viper, he asks Rick to take over a case, a task that Rick relishes until it goes sideways.

After Magnum is kidnapped, he discovers that Hannah, Magnum's ex who landed him and his friends in the POW camp, is on the island and planning to steal a fortune in gold.