I hate how they try to tell the story like it's a book where every step of the scientist is documented. In fact the story of the cult, and the cypher is far more interesting than how scientists decoded it.

In brief, a 250 years old document was decoded. It concern a German secret society : The occulist. This society pretended to be some sort of ophthalmologist while they actually more probably were trying to protect the Freemason secrets from the church.