After months apart, Tom finally reunites with his family and the 2nd Mass. But the joyous reunion is cut short as Lexi undergoes a health crisis tied to her hybrid DNA. The crisis pits family members against one another as they fight over how to deal with Lexi’s illness. Anne goes to great lengths to save her daughter.

Unforeseen opponents and new complications threaten to derail the Cardiff Electric team's work at COMDEX.

Walt is seriously concerned by Branch's behavior, but makes a key discovery in the David Ridges case. Henry faces a major setback in his trial. Vic makes an important decision about her future.

Frank Winter and his team have been recruited to work on a project even they could know nothing about until their arrival. Once inside “The Hill,” a middle class bubble on a dusty foothill in the New Mexico desert, they begin to sense that this is no ordinary assignment. In fact, they are living in a town with the world’s highest concentration of geniuses, yet it can’t be found on any map, a place where men and women are torn between duty and their moral values, husbands and wives conceal the truth from each other and their families, the military keeps secrets from the scientists they chaperone, and the scientists keep secrets from each other.

Masters delivers a baby with ambiguous genitalia and urges the parents not to surgically assign the child a sex out of fear or convenience. Meeting Virginia at a hotel for a secret rendezvous, the two of them divide their attention between sexual role-play and a championship boxing match, prompting Virginia to unearth the truth of Masters'' troubled childhood.

Ray and Abby are eager to get Bridget into her dream school, but Ray's fractured relationship with movie producer Stu Feldman stands in their way. Mickey has a date with his old flame, Claudette - but first he has to find a way around Mr. Keith, his new parole officer. Kate McPherson heads to the Fite Club to try and get information out of Terry.

After returning from the horrors of Nicaragua, panic begins to spread throughout the ship when Lt. Danny Green comes down with a mysterious illness that could be the virus. Losing faith in Rachel and her failing vaccine trials, Chandler now has to deal with a restive crew. If he fails to keep the crew together, the whole mission is in jeopardy.

Laurie's resolve is put to the test in the wake of a brutal hate crime. After his latest initiatives to maintain peace in Mapleton fall short, Kevin turns down an outside offer to rid the town of its problems. Matt brings his pulpit to the street. Meg takes on a new role.

Alison faces the aftermath of her actions; Vanessa, Darius and the president's advisors debate the next steps of the lottery. Meanwhile, Kyle and Elvis seek refuge with an old friend, until Elvis suffers a diabetic attack that puts his life in danger and threatens to expose them.

Eph and Nora fight to save Captain Redfern's life before coming face-to-face with the horrifying effects of the virus. A spike in rat attacks signals Fet that something inexplicable is happening deep below the city. Released from jail, Setrakian begins his own merciless plan to stop the spread of the disease.

Wendy and Tommy have a disastrous series of meetings. Old friends of Frederick’s from Asgard make an unwelcome visit to Fair Haven. Dash and Killian receive their inheritance which yields interesting results.