An adventurous archaeologist in the 1930s must track down and recover the lost Ark of the Covenant before it falls into the hands of the Nazis.

A swashbuckling archaeologist must find the Ark of the Covenant before the Nazis do.
(14 words)

A "high concept" version.

I don't think it necessary to include the time period, "the 1930's.? The word? "Nazis" nails the general time period.? And "Ark of the Covenant", the irresistible story hook, instantly tells how important the quest is, how high the stakes are.

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Thanks!

Spot on, nice!