When Laurel Healy returns home to Washington, D.C. to work for her brother, Senator Luke Healy, on Capitol Hill, she is caught in the midst of two huge problems: the government has stopped working due to budgetary disagreements, and mysterious bugs are eating the brains of a growing number of Congress members and Hill staffers.

Laurel continues to investigate the death of esteemed Dr. Daudier, while bugs infect more citizens of Washington, D.C. Rochelle Daudier, the deceased doctor’s daughter and Gustav Triplette, an eccentric genius, both encounter the bugs separately and begin to question exactly what is happening.

When a bizarre and deadly incident takes place on live television, Agent Onofrio's investigation into it causes Laurel, Gustav and Rochelle to dig deeper into the bug mystery. Luke attempts to cover up his affair with his Chief of Staff, Scarlett, before his opponent for the minority whip position, Senator Ella Poundstone, can make it public.

Laurel and Rochelle try to persuade Laurel’s friend Abby to get an MRI so they can uncover the real cause of the strange behavior taking over Washington, D.C. Luke attempts to reopen the government through a secret deal with the Republicans.

Laurel asks her brother, Luke, for his help to get the Centers for Disease Control and Prevention to investigate the bugs, but he insists she first consult Dr. Joanne Alaimo, a leading entomologist, for her perspective on the invasion. Laurel’s relationship with Anthony takes a drastic turn.

When Laurel is infected by the bugs, Gustav and Rochelle work quickly to figure out if there is any way to save her. When the Centers for Disease Control has its funding temporarily cut, Luke attempts to reach a compromise to have the money reinstated, but Red’s political machinations undermine him at every turn.

Laurel comes under investigation about her potential involvement with the bug infestation. Also, Gustav and Rochelle discover a unique way to communicate with those infected by the bugs.

Rochelle and Gustav capture and question a man they suspect is infected by the bugs. Also, Luke and Red face off in a Senate Intelligence meeting about a potential war.

Senator Red Wheatus hires a special investigator to dig into the Healy family’s financial and personal history. Also, when Gareth learns some sordid details about Laurel’s romantic past, it puts a strain on their budding relationship.

Laurel must work alongside an old boyfriend, Ben Valderrama, when Luke enlists her help in putting together a political documentary to support his anti-war initiative. Also, Laurel worries about the health of Luke and Germaine’s baby.

Luke and Laurel rush to uncover Red's secret agenda, which is buried in a massive new budget bill. Also, Gareth inadvertently witnesses an unsettling bug encounter in Red's office.

When Laurel discovers that a senate bill is not what it appears, she implores Luke to help, leading to a dramatic Senate sit-in. Also, Red and Ella battle for control of the bug agenda, and Laurel questions whether or not she should leave Washington, D.C. for good.

In the season finale, Laurel discovers the secret to driving the bugs out of a person's brain and tests the tactic on her father. Armed with new knowledge, Laurel and Gareth attempt to expel the Queen bug out of Red's head once and for all.