Shakespeare was not entirely accurate -- demands of drama and all that -- and in the modern day, Miranda Prospero is running the business of Prospero Inc. She receives an enchanted phoenix message from her father to warn her siblings (born after the events of The Tempest) of a danger.
And this on top of running a business to keep the oreads, nymphs, sylphs and all the elementals of the world orderly, so that they do not run wild and kill people -- it was not an asteroid that killed the dinosaurs -- and working science is feasible for humans. It's an offshoot of the Order of Solomon, which secretly expurgates magic from the historical record, so that human beings, instead of worshipping beings that it is unwise to worship for power, resort to science instead. (Which is why you do not hear of Prospero's having been duke of Milan in history, only in what you think is fiction. 0:)
But Miranda is a dutiful daughter. She gets her company gumshoe -- Mab, a wind like Ariel, but in a human body now -- to start to investigate how to track down her brothers and sisters. And within their very mansion, demons intervene, and the revelations begin. This is a trilogy particularly thick with revelations, and facts that take on new meanings four or five times as more is discovered.
Along with a roc, drinking from the Lethe, many demons and more than one unfallen angel, how the Eleusinian mysteries were an attempt to discover the secrets of cats, a magical staff made from a dogwood tree, the uncanny and untrustworthy nature of elves, and a trip through Hell. And why, exactly, Miranda is so dutiful.