Nightschool, Vol. 2 — Svetlana Chmakova

When Alex's sister, Sarah, vanishes and all memory and evidence of her
existence is erased, Alex is determined to get to the bottom of her
sister's disappearance. What better place to start her investigations
than the Nightschool itself? But when she discovers that sneaking into
the Nightschool isn't as simple as it might seem, Alex enrolls as a
student. But is she prepared for what she might find?