Even if Sydney can see the past and clasp the truth, how are we to know if he speaks it?
Agent Callo Merlose (キャロ・メルローズ, Kyaro Merurōzu?), also known as Cal, is a character in Vagrant Story. She is an agent of the Valendia Knights of the Peace (VKP), though has never actually taken part in a battle before the events of the game. Callo is a member of the VKP's Information Analysis Unit—Inquisitors—a team specializing in the collection of information, espionage, and analysis, sifting through tangible and intangible evidence for information that can help in criminal investigations. She cares deeply for those around her, even her enemies. As the story progresses, she gains the powers of a Heart-Seer. She is 23 years old and 173 cm tall.
With a Ph.D. in both criminal psychology and religious psychology, Callo entered Info. Analysis as a specialist in the analysis of cults and religious terrorism; her proficiency in information analysis has drawn the attention of the veteran analysis officers in spite of her young age. She is chosen to go with Ashley Riot to investigate the Müllenkamp attack on Duke Bardorba's home. However, she is left behind when Ashley marches in alone when the Crimson Blades launch a surprise attack.
After the events at the Duke's home, Callo goes along with Ashley to chase after the Müllenkamp leader, Sydney Losstarot who is heading to the ruined city of Leá Monde. In the only entrance to the city, the Wine Cellar, Ashley once again leaves her behind due to her lack of battle experience. When she is alone, Sydney appears before Callo and captures her. For most of the rest of the game Agent Merlose is in the hands of the Müllenkamp second-in-command, John Hardin. Hardin takes Callo and his other prisoner, the Duke's son, Joshua, to Leá Monde.
While in the evil city, the Dark begins to give Callo powers. She becomes a Heart-Seer, a witch who can read the hidden thoughts of other people. Merlose uses these powers on Hardin, revealing some of his innermost secrets before he, in desperation, stabs himself in the leg to seal off his mind. Eventually though, Callo discovers all of Hardin's secrets, and this increases the relationship between the two of them.
In the Grand Cathedral, Hardin is caught by the leader of the Crimson Blades, Romeo Guildenstern. Hardin is fatally wounded by Guildenstern but Sydney appears to his aid, teleporting Hardin, Callo, and Joshua to safety. The trio escape the destruction of the city, but Hardin dies of his wounds outside of the city walls. Callo is last seen comforting Joshua and watching Leá Monde collapse.
In the final scene of the game, Ashley uses his powers to disguise himself as Callo to avoid capture.