Synopsis: Differential Integral (a Sir Differel adventure)

The girls are mall-crawling one day, when they go in a newly opened knick-knack shop. Sunny finds a darling figurine but can't find a clerk. She goes into the back and finds a young woman strapped to a chair, barely conscious. The girls release her, but are assaulted by a demonic dog-like creature. It chases them out into the mall, but is intercepted by a large man dressed in red wielding two huge pistol. He orders them to get the woman away while he engages the beast. On their way out, they run into Shasta Taffaday. When the beast attacks, Shasta covers them as they make for her car. At the last second, the large man reappears and grapples with the beast, making it possible for them to get away.

They go back home and get the unconscious woman in bed. They then call Wendy Cleasa and Medb. Medb does not answer, but Wendy agrees to come right over. While they wait, Dolores Cadera-Hueso stops by to question them about the incident at the mall. When Wendy arrives, she wants to take the woman to a hospital, but the large man shows up and forbids it. He introduces the woman as Baronetess Sir Differel Isolde Churchill Pendragon Van Helsing, and himself as Dracula. He explains that he came to America to rescue her, but he doesn't know who took her. Therefore, it would be dangerous for her to go to a hospital, where she could not be protected. Dolores offers police protection, but he sneers at that. However, he is willing to trust the girls, though he refuses to explain why. Dolores agrees to keeping her there only because the evidence suggests that this is not a usual police matter, and she agrees to get whatever Wendy needs to care for the woman. Dracula leaves, explaining he must find out who tried to kidnap Sir Differel.

As Wendy cares for Sir Differel, Annis Nin comes by. She explains that Medb is unavailable, but that she asked her to respond if the girls needed help. She is followed by Ceithlenn, in human form, who explains who Sir Differel is. She admits that the Fomorians are enemies with her, and if possible would take her or kill her, but her agreement with Medb prevents her from acting. However, she warns that other Fomorians may try, and while she will intercede for the girls, she cannot guarantee to stop them. Annis, Dolores, and Shasta realize they may have a fight on their hands, but Dolores is reluctant to involve the police. So they arm themselves with weapons Annis carries in her SUV.

Meanwhile, Sir Differel awakens, but is completely paralyzed except for her eyes. Sunny establishes that she understands Morse code and she confirms everything Ceithlenn said. Another visitor arrives, a monsignor. He asks for custody of Sir Differel, explaining he can protect her, but Sir Differel tells Sunny he is not a friend. When they refuse to give her up, he politely threatens them, but becomes more antagonistic when Ceithlenn reappears. The girls realize both parties want her, and use that to hold them off. Ceithlenn and the Monsignor agree to the standoff, but only if they can remain.

They contact Mabuse to find out how to counteract Sir Differel's paralysis. They take a blood sample and smuggle it out using Kitty. Kitty returns later with Dr. Joyce Luasaigh, who has the antidote. She's also there to support the girls. That gives them the idea to call in reinforcements. They contact Pastor John Sjauken and Kojoro, and ask Mariam Alina-Fuad to come by to help Wendy. They all agree and arrive before nightfall.

At dusk, Uallach Ruadhrion arrives. Uallach explains that the vampires also want Sir Differel, but their agreement with the girls also prevents them from acting. Uallach insists on staying to counter the Fomorians and the Vatican. To balance their own forces, the girls contact Giovanna Mencia Borgia. Though at first reluctant to go against the Conclave, she agrees to help them keep the peace for their sake.

Later, after Sir Differel shows signs that the antidote is working, Liadan Fionuir appears. She announces that the house is surrounded by vampires, Fomorians, and Vatican agents, besieging them. She also explains that there is a fourth party involved, an ancient evil older and more powerful than even the Fomorians, that seeks to reclaim its one-time dominance of the world. She agrees to stay and lend her support to the girls.

In the morning, a Fomorian, vampire, and Vatican commando are found dead. Ceithlenn, Uallach, and the Monsignor blame each other. When dawn comes and Uallach does not go into torpor, the girls explain that Mabuse developed a drug that could suppress the circadian rhythm, though it is not without its side effects. This causes distress for Ceithlenn and the Monsignor, who had assumed the vampires would be helpless during the day. Tensions mount as the surrounding troops get nervous. Meanwhile, Sir Differel completely recovers. She explains that she had been kidnapped from her headquarters and taken to America, but remembers few details. She tries to summon Dracula to take her back, but for some reason cannot make contact with him. She must wait for him to return on his own, and even then the question becomes whether he can get her out without causing a bloodbath. She tries to bluff, but Ceithlenn, Uallach, and the Monsignor are not cowed. Attempts by Pastor Sjauken, Dr. Luasaigh, and Kojoro to intercede go unheeded. To stall for time, the girls offer to mediate negotiations between Sir Differel and her three enemies. Ceithlenn and Uallach have no choice but to agree when the girls state that Sir Differel is under their protection and they will fight to protect her. The Monsignor is not impressed, but the other two pressure him into agreeing; his assembled commandoes cannot fight both Fomorians and vampires together.

The negotiations run until nightfall, making some progress. The parties agree in principle to avoid bloodshed, so as not to involve the police by harming innocents. They also agree in principle that the best way to accomplish this is to let Sir Differel go. However, it is clear that her three enemies wish to gain concessions that will give them certain advantages. Sir Differel is just as adamant not to grant any. After the three enemies have left the house, the girls and their friends try to get the different parties to bend, but with little luck. They do, however, find a way to relax that relieves tension.

Ceithlenn, Uallach, and the Monsignor meet in private. Despite mutual suspicion, they can agree they want the same goal: the neutralization of Sir Differel. Since control by one party is undesirable to the other two, and she cannot be controlled by all three, they agree she must die, before Dracula shows up. They must get her away from the girls to do that, so they decide to fake an agreement that will get Sir Differel out of the house, then they can isolate and kill her. Her organization will destroy itself from infighting.

During the night, someone attacks the occupants of the house. Though no one is seriously harmed, the attacker gets away. There is no agreement on who it was, with claims that it was a vampire, a Fomorian, or a commando. Sir Differel is convinced her enemies are planning treachery, and the friends back her up, but the girls are suspicious. They also learn that each group surrounding the house has itself been attacked, resulting in a three-way skirmish before the three leaders can get them under control. The girls realize that it must be Liadan's fourth party trying to start a war.

Negotiations begin again in the morning. By noon break, things look promising. The three enemy leaders back off from their more hard-line demands, allowing Sir Differel to make minor concessions. To unwind while waiting for lunch, Sir Differel spars with Annis, fences with Shasta, and participates in a shooting match with Dolores, demonstrating that she is an expert martial artist, a skilled swordsman, and a crack shot. Negotiations begin again after lunch and by mid-afternoon an agreement is almost in place. Sunny goes down to the basement to collect a bottle of champagne to celebrate. She finds an intruder about to kill Giovanna while she's in torpor. It attacks her and she sees it is an anthropomorphic serpent. As it leaps at her, it is intercepted by Dracula, who rips its head off. He then proceeds upstairs to present his trophy to the assembled people. The revelation stuns everyone, though Eile isn't sure what the three enemy leaders find more disconcerting, the serpent man head, or Dracula's presence. It is clear to her, though, that Uallach and Ceithlenn recognize it, and understand its implication. The Monsignor, however, declares it a hoax and demands Sir Differel's immediate surrender. Uallach and Ceithlenn object, and the three quarrel until Dracula announces in a bellow that any attempt to take Sir Differel will result in all their deaths. The Monsignor is not impressed and gives Sir Differel 24 hours to surrender or he will storm the house. He then leaves. Eile knows that that will precipitate a battle as the vampires and Fomorians attack the Vatican commandoes, both to deny them their prize and to protect the girls. Realizing that the Monsignor will use the time to bring in reinforcements, Uallach and Ceithlenn depart to increase their forces as well.

Dracula reveals that he can get Sir Differel out without bloodshed, in secret, but that won't stop the Vatican commandoes from attacking. Besides, as long as the real enemy is loose, Sir Differel is not safe anywhere. He describes how he discovered the identity of the real kidnapper, an ancient Serpent Woman scientist and wizard known as Leannán Soit, but was unable to locate and deal with her. Sunny wants their friends to leave for their safety, but they refuse to go, and Dracula states they are in fact safer in the house. Alternatively, Eile suggests they hole up in the safe room in the basement, but Dracula states that the Serpent People can get in there as well. With their power of illusion, there might even be one in this room right now. He grins as the humans all look at each other with suspicion, but Eile notices he is impressed when Sunny convinces them they must trust one another. The girls confer with Sir Differel, Dolores, and Annis on the best way to defend the house.

When Giovanna awakens, Dracula reveals that she is a Draculina, that it was he who had given her his blood first before Lucas Cornelia usurped his claim. As such, while diluted, his blood would make her as powerful as he. For example, like him, she could resist the torpor and go out in the daytime. Though she is skeptical, he trains her through the night. Towards morning, a murderous attack is made on the house. Led by Dracula, the armed women, Giovanna, and Sir Differel defend the others. The attackers turn out to be Serpent People, though of a decadent, devolved sort. No one is killed, though there are some injuries. Strangely, no one outside seems to realize an attack is in progress. When the fighting is concluded, Giovanna realizes it is past sunrise, yet she has managed to stay awake. Eile notes that Dracula seems proud of her, though he feigns sardonic indifference.

After everyone recovers, Sir Differel decides to confront her adversaries. Going outside, accompanied by Dracula, the girls, and their friends, she demands a truce to deal with their common enemy. The Monsignor is still unconvinced, even after being shown the bodies from the attack. When he demands proof, Sir Differel nods to Dracula. Grinning, he shots Liadan at pointblank range. The slug throws her back, but it doesn't kill her, and at the same moment she transforms into a Serpent Woman. She grows larger and attacks Dracula as more Serpent People attack the surrounding forces. Soit actually tears Dracula in half. When shooting bullets does no good, Sir Differel conjures a sword from thin air, which seems to give her an advantage, along with Dracula still attacking even though he's in two pieces. But Soit manages to grab Sir Differel and start to carry her off when helicopters appear overhead. Armed men rappel down ropes and Medb jumps a hundred feet to the ground. She engages Soit, who drops Sir Differel. A reconstituted Dracula joins in the fight as the girls pull Sir Differel out of the way. Medb and Dracula manage to subdue Soit, but she disappears in a flash and cloud of smoke.

The reinforcements turn out to be a combination of Medb's mercenaries and Sir Differel's commandoes. Though there are casualties, the Serpent People are all killed or driven off. The four armed groups then face off against each other, but the girls put themselves between them and force them to back down, appealing to the need to tend the wounded and collect the dead. Sir Differel, Ceithlenn, Uallach, and the Monsignor call and truce, and after they collect their casualties, evacuate, leaving Medb and her mercenaries in charge. Dracula then takes Sir Differel home, but not before she thanks the girls and their friends for their help. The mercenaries sweep the neighborhood to find any straggling Serpent People as a team moves in to clean up. When Dolores remarks her wonderment that the neighbors hadn't noticed a thing, Medb explains that between Soit, the Fomorians, and herself, they were able to enshroud the house with illusion, so that no one would notice. Before seeing their friends off, Sunny invites them all back for Thanksgiving dinner, which they accept.