War of the Fae (Book 9, Dragon Riders)

Jayne has returned to the compound, but that's the last place she wants to be. She desperately needs to go back in time to rescue the friends she left behind, solve the problem in the Overworld, and fulfill her duties to Biad at Uamh An Ard-Achaidh, the High Pasture Cave in Torrin on the Isle of Skye...but the Council has other ideas about where she should be and what she should be doing. Unfortunately for them, she's never been good at following orders or ignoring what her heart tells her. She might get more than she bargained for, though, when she takes matters into her own hands and jumps headfirst into the dangerous world of dark spellcasting without any backup.