The son of a family of devout Jehovah's Witnesses is accused of killing his teacher after being caught fleeing the scene of her murder. Meanwhile, the team is hired by the Democratic National Committee to investigate a second case in which the Chairman of the House Ethics Committee is accused of paying for sex.

The murder of a teenage girl – who is the daughter of a powerful federal judge – leads The Lightman Group to a highly competitive college-prep school where getting to the head of the class means everything. The team also investigates a NASA test pilot accused of intentionally crashing a $250 million aircraft

At a state wedding, Lightman and his team work to prevent the assassination of a South Korean ambassador. But when someone else is shot, Lightman exposes long-held family secrets and lies to identify the assassin.

Lightman and Torres interrogate an imprisoned gang leader who claims to be rehabilitated. If the gang leader is freed, he might help fight inner-city violence or return to his life of crime. Foster and Loker investigate the death of a firefighter who was killed in the line of duty.

Lightman and Foster investigate the disappearance of an 11-year-old girl who may have been murdered. Meanwhile, Loker and Torres must determine whether a famous peace activist is who she claims to be and if her bestselling memoir is true, but Loker's attraction to the socially conscious woman may be clouding his assessment of her.

When Lightman is hired to find a corporate spy at a pharmaceutical company, he discovers a high-level conspiracy surrounding a new drug that could put thousands of lives at risk. The team is also hired by the State Department to assist with negotiations for the release of two Americans imprisoned in Yemen.

Lightman becomes obsessed with his investigation of two young women who committed suicide. Meanwhile, the team tries to recover billions of dollars for investors who were bilked by a Ponzi scheme.

In the wake of a building collapse in a small town outside Washington, Lightman is brought in to determine who is at fault, and he discovers a massive cover-up. Meanwhile, the team is hired by a "dot-com" billionaire to determine if his girlfriend loves him for the right reasons.

When Assistant U.S. Attorney Zoe Landau, Lightman's ex-wife and Emily's mother, enlists Lightman to help investigate an arson case in which the only eyewitness is a 5-year-old boy, it quickly becomes clear that she and Lightman still have feelings for each other. Meanwhile, Foster and Torres question a rapper who is suspected of murder.

The Lightman Group gets embroiled in the controversial case of a policeman who shot a potentially innocent teenager. Meanwhile, investors who were bilked by a Ponzi scheme are suing The Lightman Group for botching the recovery of their money,

Ben Reynolds, an FBI agent who's been pursuing a serial rapist terrorizing the Washington area, partners with The Lightman Group for its toughest case yet. Lightman infiltrates a prison to befriend Andrew Jenkins, a convicted criminal and a pathological liar who the serial rapist may be copy-catting. Meanwhile, Torres and Loker search Jenkins' fan mail, and Foster questions one of the rapist's recent victims.

After a terrorist bombing outside of Washington, DC, FBI Agent Ben Reynolds calls on The Lightman Group to help identify those responsible and prevent more attacks. The case takes a personal turn for one member of the team and begs the question of whether honesty is indeed the best policy. Zoe helps Lightman with the investigation and both are concerned about their daughter's safety.