During Harry's first time in the Restricted Room at Hogwarts, he encounters a screaming book that reveals his presence to the guard. Harry uses the invisibility cloak to avoid detection.
The team deciphers the remainder of the coded message, giving them the location of the THABTO's meeting. They discover the time by having Ghostwriter speedread the Double Defenders books.
Jamal explains what they know about Ghostwriter to Alex after Ghostwriter writes a message to Alex. Jamal then deduces that THABTO is connected to a series of backpacks being stolen.