Toxic - Pretty Little Liars, Bk 15 Author:Sara Shepard High school seniors Aria, Emily, Spencer, and Hanna barely survived their most recent encounter with A. And it's not over yet…. The police don't believe there's another, deadlier, A out there, but the girls know what-and who-they saw. If they don't track down this final tormentor soon, A will silence them forever.