Robert Crain is a Germanpacifist living in India during the Second World War. He is blackmailed by the Allies into using his demolition expertise to cripple a Nazi ship carrying rubber from Japan. The Allies hope to recover the ship before it is scuttled by the Captain because rubber was in short supply and essential for various uses in the war effort.
The film did not do well on its original release, probably at least in part because few people understood its title. In an attempt to be more commercial, the film was reissued as "Saboteur: Code Name Morituri".
The title "Morituri" is the plural of a Latin word meaning "about to die". Urban myth (not academically agreed) suggested that Roman gladiators in the arena would begin their battles with "Morituri te salutamus" or "Morituri te salutant" (We/They who are about to die salute you). (See WIkipedia's article on this expression: Ave Imperator, morituri te salutant)