Professor Armitage and others have been bitten by Cardinal Ferencz (pronounced "fang" in his thick generic European accent) and have fallen into comas at the hospital, as his bite devours their blood from within. The Prof, in fact, has already been pronounced dead and his body stolen, although Dr. West, who declared him dead, turns out not to be the most reliable witness. Alexandra thinks some sort of sorcery might save the others, but if something isn't done, they will be dead within hours and vampires three days later.
Diligence tries reconning in the astral realm and finds Charles Anton White, one of the sleep experimenters, ensnared by coils of spiritual thorn bush. He rips it loose, which causes White to die immediately, then wake up as a vampire! He belts Walker across the room, as all vampires are apparently required to do by the Vampire Code of Conduct. Billy, who has just exerted tremendous effort to exorcise Cardinal Ferencz's taint from Thessaly, is too dazed to open the windows (it's early in the morning, with plenty of sunlight outside), so Thessaly whaps him with her IV stand, which just makes him mad. Alexandra uses the Runestaff to weaken White's body, and suppresses his vampire blood completely, returning him to dust.
Thessaly says she remembers being bitten by Cardinal Ferencz, and seeing Dr. Armitage mixing up some sort of potion in the corner of the room, apparently working with the Cardinal willingly. She didn't notice if he was a vampire yet or not.
Alex uses the Runestaff to trace the Doc, using a sample of his hair they gleaned from his apartment on an earlier occasion. This time it leads to the northeast of the campus, straight to Doc's office in the Medieval Metaphysics building. Diligence, holding forth on the importance of checking corners, goes up the stairs first and is flattened by a kick that would have killed him but for some quick first aid.
Several of the Blood Dolls, girl ghouls now made full-fledged vampires, are helping Dr. Armitage gather some magic gear from his own office. Dr. Armitage hurries past Billy; he doesn't look like he's going to make it, until he shouts, "Kill the girl!" and Billy bounds up the stairs to see a vampire about to bite Excellence. The vampire goes flying out the window.
Juliet is up against a white-haired Chinese girl named Mink, whose fingernails are abnormally sharp and teeth are quick and nasty. She rushes Mink out the window, too, falling four stories to hit the lawn with a new appreciation for gravity's majestic might. Being the Slayer, however, she doesn't die.
Alex, Juliet, Walker and Billy are the only ones left to follow the Doc and his surviving escorts into, what else, the cast-iron 1920s storm drains. They follow to a room under the Freeman Building (history and rare books) and listen while the Cardinal explains that all is now in readiness to receive his six colleagues from the other six Sabbat clans. They will be able to choose the Antipope free from interference of the Slayer, now that they have turned Dr. Armitage to the Dark Path. Billy is not surprised to hear Moonstomp's voice in league with the Cardinal. Once they hear Moonstomp leave, Walker and Juliet are up the ladder and into the room.
Dr. Armitage is armed with a metal crescent from which is suspended a teardrop, or blood drop. This is the Mark of Cain, which affects creatures of the natural world the same way the Cross affects vampires. Walker is forced away by its unholy radiance, driven into a working fireplace, where he catches fire. The Cardinal cloaks Juliet in living darkness which strikes with a hundred hands from all sides. Billy confronts Dr. Armitage and sticks a knife in him before he can turn the Mark of Caine on him, then kicks the Mark into the fire from which Walker has painfully emerged.
Juliet defeats the Darkness, and the Cardinal escapes. Alex, with great effort, exorcises the Cardinal's taint from Doc's bloodstream. Dr. Armitage is able to tell our heroes that the other six cardinals are due to arrive soon, but that at Armitage's advice the Cardinal has given up biting mortals and started instead turning ghouls into vampires. Ghouls, Dr. Armitage reasons, are already evil, and in order to turn them the Cardinal has to give them some of his precious blood, weakening himself. He's only got two Blood Dolls (Skeeter and Howler) left, plus Moonstomp and himself. We should be able to handle four vampires before their friends get here, eh?
Then he collapses from shock and blood loss, of course, having fulfilled his mission to explain what's going on.