Why did leontes want Hermione to meet the king polixenes and why did he become jealous

Without any good cause, Leontes, King of Sicilia, suddenly comes to believe that his wife Hermione is having an adulterous affair with his best friend Polixenes, King of Bohemia. He orders Camillo, his trusted friend and advisor, to poison Polixenes. Camillo is torn between loyalty to his king and following his conscience. He chooses his conscience, and rather than obey his king he helps Polixenes to escape back to Bohemia.