What is the main conflict in The Magician by Michael Scott?

In this novel, twins Josh and Sophie find themselves suddenly transported to Paris moments after escaping Dr. John Dee in Ojai, California. Sophie, whose magic has only just been awakened, is exhausted from her efforts in helping them escape first Dr. Dee and later, Niccolo Machiavelli. The twins are finally offered a few minutes to decompress and begin thinking about all that has happened to them. Josh is worried that he cannot trust Flamel while Sophie is all too willing to accept everything that is happening around them. When Dr. Dee and Machiavelli attack again, this time with Valkyries and an ancient monster, it does not seem that it matters which immortal they can trust but whether than can survive creatures that are not even supposed to exist. The Magician is an exciting second installment in the Flamel series that will leave readers begging for more.