The Sorceress by Michael Scott (2009) Ember

Being the third volume of The Secrets of the Immortal Nicholas Flamel.  The story of the twins continues with the Sorceress held captive on Alcatraz, guarded by a Sphinx who can drain her magical energy.  But Perrinelle has other talent – she can see and converse with ghosts.  Even though she has spent much of her long life blocking out their entreaties, now she needs them.  The primary candidate for her purposes is the ghost of the Spaniard who discovered the island and returned after his death because the view from the island was so beautiful.  He leads her to a spider goddess who is held behind wards.  Perry and the spider know each other and agree to work together, so Perry frees her from her prison, but decides to carry one of the spears that held her.  The spider helps Perry capture the Morrigan who has come to kill her.  Once the Morrigan is in the spiders’ former cell, Perry bargains and gets the Morrigan’s other personalities to take over and become an ally also.  This is necessary because Billy the Kid and Machiavelli are coming to kill Perry.  In the meantime, the twins are taken to London to see Gilgamesh so he can teach them about the magic of water.  Dr. John Dee failed to capture them in France, but England is his territory.  The twins want to return to America and the place to do that is Stonehenge.