<Li> Christian Kane as Jacob Stone, an Oklahoma laborer and genius with an IQ of 190 and an extensive knowledge of art history and architecture . Fearing disapproval from his family, he has hidden his talents from them . While he initially does not trust Cassandra after her betrayal in "And The Crown of King Arthur", he eventually accepts her as a valued member of the team . </Li> <Li> Lindy Booth as Cassandra Cillian, a mathematician who has auditory and sensory hallucinations linked to memory retrieval, as well as a rare condition called synesthesia . She has a brain tumor, diagnosed in childhood, which causes pain if she thinks hard enough . Because of the extreme pain, Stone has taught her to connect to a peaceful memory during her thoughts . </Li> <Li> John Harlan Kim as Ezekiel Jones, an Australian thief, "master of technologies" and fan of classic crimes who enjoys playing the role of international man of mystery . He is an expert thief, having hacked the London Police's security network, NSA, and numerous other law enforcement agencies . He prefers to rely on his luck and wit, not showing much concern for others until he gets to a point of realizing something important about the current case . </Li> <Li> John Larroquette as Jenkins (Galeas / Galahad), the Annex's reluctant, sometimes cantankerous caretaker; he has worked there "for longer than anyone knows" and has extensive knowledge of ancient lore . He is also seen to have a connection to Dulaque, as revealed in "And the Apple of Discord". It is later explained that they are both immortal because of a spell Dulaque cast 1,000 years earlier after the fall of Camelot . He was known during King Arthur's reign as Sir Galahad, as revealed in "And the Loom of Fate". He has also known Morgan le Fay (Alicia Witt) for centuries and considers her to be his archenemy, as he blames her for Arthur's death . </Li>

The cast of the tv show the librarians