Casaubon
As the protagonist, Casaubon dictates the pace of the plot. He is a young man fascinated, nearly to the point of obsession, with the occult and mystery. In college in writes about the Templars. Although he devotes some years to the pursuit of romance and family, he is dragged back into his post-grad world through work. He works closely with Allier, but sees through the man's shallow guise of charity. As the narrative progresses, Casaubon loses the power of volition. He no longer wants to pursue the conspiracy, but his very life comes to depend upon it. By the end of the book he is locked in his home alone, waiting for Allier or one of his co-conspirators to murder him.
Amparo
Amparo is a Brazilian native who falls in love with Amparo. She's a nature lover, fueled by revolutionary Marxism. Her diverse opinions are why Casaubon loves her. After having a bad trip during a magical ritual one day, Amparo loses herself. She's deeply disturbed by the experience and somehow blames Casaubon, dissolving the relationship.
"Garamon" Belbo
Belbo is the editor of a local publishing house in Milan. Meeting Casaubon while he was still in college, Belbo takes a liking to the younger man's curiosity and intellect, inviting him to work for him later when he owns his own paper. He invites Allier from Brazil to consult for his paper, until he becomes insanely jealous of the man in his private life. Belbo is the one to reveal the secret Templar plans to Allier and his companions, but he's rewarded with torture and death at the pendulum site.
Leah
Leah is Casaubon's second girlfriend. She gives birth to their baby right around the time Allier turns into a victim, so she represents a liability to Casaubon. He sends her and the baby away to the mountains, even after the events are wrapped up.
The Colonel
This man is a retired colonel who appears on the newspaper doorstep one day with information about the Templars. He reveals the orders secret plans to Casaubon and his friends. Shortly afterward he mysteriously disappears, never to be seen again, presumed dead.
Diotavelli
Diotavelli works with Belbo when Casaubon meets him. He represents the third member of their trio, intent upon discovering Templar secret. Of the three he is the least dramatic and offensive, often positioning himself as peacemaker. Tragically Diotavelli gets cancer before the adventure is over and dies in the hospital.
Mr. Allier
Originally from Brazil, Allier is hired by Belbo as a consultant at his paper. He quickly convinces Casaubon to confide in him about the Templar conspiracy because of his extensive knowledge of the occult, although Casaubon has his reservations. Allier turns out to be a villain, intent upon exploiting the Order of the Knights of the Temple for his own profit. After recruiting all kinds of cultists, criminals, and the like, Allier forces Belbo into giving him the colonel's information, the key to solving the Templar mystery.
