After starring in three adventures, the inimitable quartet of Reynie, Sticky, Kate, and Constance haven't had a mission together in some time. But with the arrival of a new Society member--and a new threat--they must reunite to face dilemmas more dangerous than ever before, including the return of the villainous Mr. Curtain and his Ten Men and a formidable enemy with a mystifying ability to track their every move.