The Crimson Spell — F. Goldsborough

Evil thoughts and dark desires Boil and burn in a wicked brew! Throw bate and fear into the fire -- May friends and lovers both be true! Prue, Piper, and Phoebe don't know that a coven of warlocks is hunting them. They don't know that one of the warlocks has entered their lives disguised as a friend. And they don't know the coven's mission -- to drain them of their magical powers, even if it means destroying them to do it! Now the Charmed Ones must figure out which of their friends is really their enemy. Because sometimes what you don't know--can kill you.