Sally Forrest in Son of Sinbad (1955)

Sinbad was pursuing a secret weapon: Greek Fire. Attributed to the ancient Greeks, it was composed of pitch or bitumen, sulfur, and other ingredients. It was used in naval warfare and the Romans also made use of it but with the fall of the ancient Western world, it was temporarily forgotten, but it was rediscovered by the Arabs from whom European Crusaders also learned the method of making it.