On the ride home from school, Avery researches the phrase fruit of the poisonous tree and learns that it refers to a legal doctrine about illegally obtained evidence being inadmissible in court. Jameson notices that Avery is thinking through a lead, but Avery refuses to reveal her reasoning because Jameson might try to solve the puzzle first.

After arriving at Hawthorne House, Avery goes to her wing and waits before opening a secret passage hidden behind her fireplace. Jameson is already waiting inside, having correctly guessed that Avery is heading back to Toby Hawthorne's sealed wing. Avery lets Jameson come along but warns Jameson not to get caught by the Laughlins.

Avery returns to Toby's study and searches the bookshelves again, this time focusing on Toby's law books rather than hidden compartments. The phrase from William Blake's poem leads Avery to the legal section, and Jameson quickly realizes that Avery is using fruit of the poisonous tree as the clue.

In a legal book, Avery finds the entry for the doctrine. Certain letters and punctuation marks have been blacked out across several pages, forming a hidden message. Avery records the marked letters on her phone, but the resulting string of characters makes no immediate sense.

When Jameson pushes for what Avery knows, Avery admits that Avery found a cipher disk but does not know the code. Jameson immediately concludes that they need numbers. Avery remembers the clock where Avery found the cipher and sees that its hands are frozen at twelve and five. Jameson identifies the corresponding letters as L and E, and Avery runs back to her room for the cipher disk.