Glenbrook (The Ethereal Crossings, #4‪)‬

Luke is trapped in Shadeland, and there’s supposedly no way to get him out. Everyone is keeping their mouth shut, since something’s happening within the Eidolon world that they don’t want the humans knowing about. Not only that, Yamuna has escaped her prison on Glenbrook and SILC is at a loss for what to do. Agent Eyre warns Liv to stay out of it, but the secrets coupled with Luke's vanishing act has her at her wits end.

Liv is determined to save Luke and find out what the Eidolon are hiding, even if it means going against all warnings, and travelling to Shadeland herself.