"There were only around for a couple of hundred years but they were very big in terms of helping pilgrims to get to the holy land, protecting them," said Father Thomas Williams. "They were kind of like an order of bodyguards."
But history books painted them as villains - with the Catholic Church casting them out, many of them tortured and burned, branded as heretics, CBS News correspondent Richard Roth reports.
When novelist Dan Brown imagined them to be the super-secret guardians of the holy grail, his version of their story had no trouble finding buyers.
Now, from the Vatican comes the official story. Bound in leather and sealed with wax, copies of an epic called "The Trial of the Templars" are now on sale in Rome.
Misplaced in church archives and overlooked for centuries, the document they're based on was an accidental discovery.
"It's a needle in a haystack thing. Everybody wants to be the one to finds the document that makes history or changes people's opinion of things - and this is one of those," Williams said.
It's a 700-year-old parchment record of a Vatican trial, with the Knights Templar found guilty of violent crimes and corruption - but never convicted of heresy. They didn't lose their job for lack of faith.
Fierce fighters, wealthy and almost certainly corrupt when they were disgraced and disbanded by the church they'd served - the knights, it turns out, may have simply been victims of 14th-Century politics: set up by a French king who wanted their riches and a Pope who couldn't protect them.
But this story's only out in a limited edition.
Just 800 luxurious copies of the ancient Vatican original have been produced, and one's already gone to the Pope. The rest are sure to sell out, but at more than $8,000 a piece - this could be the season's most expensive new read.