Contains spoilers for this episode and earlier episodes.
The murder of Danielle Stark takes Lightman and Torres into a prep school where grades and university admissions dominate the students' lives. Danielle's mother, a federal judge, seems to be concealing something, but her alibi holds. Interviews with classmates uncover the use of prescription stimulants to improve test performance. The investigators then discover a stranger result: Danielle's entrance-test score improved after her death, pointing towards someone taking the exam in her place.
A teacher admits taking the test but initially claims Danielle hired her. Security footage shows that Danielle did not understand the arrangement when they argued. Her mother actually paid for the cheating, and Danielle threatened to expose it. The inquiry reaches Riley Berenson, whose father tries to confess to the murder himself. Lightman challenges his account, and the father admits that he was protecting Riley. She is taken into custody.
Meanwhile, Gillian and Loker investigate test pilot David Markov after he crashes an experimental aircraft. He denies knowingly taking medication, and his wife finally admits secretly giving him an anti-anxiety drug because his ambition had damaged their family life. At home, Lightman catches Emily lying about a sleepover that was really a large party. She cleans the office as punishment, then reminds him that being able to catch some lies does not mean he understands everything about her.