11. 2πR

Complete story — includes the ending

With Reese in FBI custody, Finch poses as a high school teacher to protect the next number, a teenager named Caleb Phipps who is deliberately underperforming at school to hide his intelligence. Finch discovers that Caleb is a master coder and, with Fusco's help, learns the boy is also a drug lord. Finch accuses Caleb's tech teacher of stealing Caleb's code, but the truth is that the teacher is trying to promote Caleb's work so investors can help Caleb profit from it. Finch learns Caleb plans to give his valuable code and drug money to his drunk mother and commit suicide at the train station where his brother was killed in a train accident. Finch is able to talk Caleb out of it. The next day, Caleb thanks Finch as he prepares for school, as Finch hints about his own past as a legendary hacker. Meanwhile, Reese and three other men are held captive by the FBI, who prepare to interrogate each one until they reveal the identity of the "Man in the Suit". In order to help prevent this, Carter removes Reese's fingerprints from the system and tampers with the DNA evidence.