Infinite Regress — Christopher G. Nuttall

Emily returns to Whitehall, only to discover that things have changed. The new Grandmaster doesn't want her in his school - and is only willing to accept her as a probationary student. If she wishes to remain at Whitehall, she must work for Professor Locke as an assistant while managing her studies and her growing relationship with Caleb. And, as if that wasn't enough, she is also expected to mentor a bunch of younger students. Her time is no longer her own. But when Professor Locke starts opening the tunnels under the school, hunting for the lost secrets of Old Whitehall, he triggers off a series of catastrophes that threaten to tear the school apart. As the staff and students struggle to survive, Emily is forced to solve a disturbing mystery... ...And figure out what it has to do with her private research.