A routine flight aboard the airship Tristan turns deadly when the craft is hijacked by the vampire Alfred, a member of the radical group, Fleurs du Mal. Unless Alfred's demands are met, he intends to crash the Tristan into the heart of Rome. Only Abel Nightroad, a passenger on the ship and a touring priest for the Vatican, stands between the vampire and the destruction of the Holy See.

While investigating the activities of the Fleur du Mal, Father Nightroad encounters a young girl with strange and dangerous abilities. And when the girl attempts to flee, Abel must turn against his own comrades in order to save her life and prevent her from falling into enemy hands.

Abel Nightroad journeys to Ishtvan, a city where the tenuous balance of power between the Human and Vampire worlds is threatened. With the vampiric Count Gyula secretly preparing a weapon of mass destruction and the Vatican's Sister Esther carrying out her own personal war, Abel finds himself caught between a rock and a hard place.

With Esther and Abel his prisoners, Count Jula reveals his plan: to use the Star of Sorrow to rain destruction down on the human race in revenge for his wife's murder. But the mysterious order of Rosen Kreuz has its own plot for twisting Jula's scheme to achieve their evil ends. If Abel can't stop them, the world could face Armageddon all over again.

Father Abel Nightroad escorts Sister Esther to Rome, where she meets Lady Caterina Sforza. While there she also meets William Walter Wordsworth, Father Havel, and Sister Noelle Bor, who all do their part to welcome her into the AX. While lost on the grounds, she encounters a young boy crying, who later turns out to be Pope Alessandro. With this being her introduction into the ways of the AX, has Sister Esther gotten herself into more than she can handle?

A murder on holy ground has taken place in Amsterdam, and Lady Caterina sends in the mysterious Father Hugue, also known as "Sword Dancer", to investigate. The local leader of the vampires, Cabel, knows the he and his followers are not responsible, but only the unconscious memories of Agnes can help him prove it. But with so much at stake on the investigation's outcome, no one can be trusted and no one is safe.

When ships off the coast of Albion are attacked by what appear to be vampire fairies, Abel seeks out an old comrade, Leon, a former A.X. member now doing hard time, to help him investigate. In exchange for his assistance, Leon will get his prison sentence reduced--assuming, of course, either of them survive their assignment...

During a state visit to Londinium to attend the funeral of the Queen of Albion, Esther and the Pope are trapped in the underground factory known as the Ghetto when vampire terrorists attack. The A.X. team races to save them, with the grudging assistance of Petro and Paula of the Inquisition...and depending on Abel's mysterious knowledge of the Lost Technology...

Death Hunters attack the vampires of the underground Ghetto, as Petro battles to lead the Pope to safety. Abel faces off against Dietrich...and against someone far more powerful, and closer to him than he could've expected...

Cain, having killed his brother, Abel, plots with Kampher to destroy the people of Rome and, soon after, the world. The Vatican and the kingdom of Albion join forces to fight against them. Virgil reveals an important secret to Esther that will forever change her destiny. Will she be strong enough to accept it and use it to help the people of Londinium?