Riley, Maya, Lucas, and Farkle start their freshmen year and quickly learn their place as smaller fish in a much bigger lake.

Weird Al Yankovic signs on as band leader and guest Kevin Bacon leads a tour of Kevin Town. Also, a leprechaun hassles Scott.

Kyle Barnes deals with a demonic possession case that causes him to look into the secrets from his own past.

After listening in and hearing Bobo mention an archenemy, Wynonna and Xavier go to the Pine Barrens Dolls make their way to the snowy Barrens to find the weapon that makes Bobo's nemesis so dangerous. Meanwhile, Doc learns how to drive after Wynonna gives him Constance's car.

Bill's guests include Hayden Planetarium director Neil Degrasse Tyson, "Double Cup Love" author Eddie Huang, Daily Beast editor-in-chief John Avlon, venture capitalist Nick Hanauer, and Reason magazine's Matt Welch.

The Lonely Island shows off their new merchandise; Gil Faizon and George St. Geegland discuss their upcoming Broadway show.

Heroin Crisis - America is facing the worst drug epidemic this country has ever seen: more people are dying from overdoses than from car accidents-and at the center of it is an explosion in the use of heroin. Thomas Morton traces the causes and impacts of the crisis, from the poppy farms of Mexico to the hills of West Virginia, and investigates how users, first responders, and government officials are responding to the new reality of American drug use.

New Age of Nukes - Twenty-five years after the end of the Cold War, America's vast nuclear arsenal is beginning to show its age, and the government has embarked on the largest nuclear modernization effort in our history, costing American taxpayers as much as $1 trillion. Kaj Larsen goes aboard a ballistic missile submarine and visits the facilities on the front line of our nuclear weapons program to see why the military wants to upgrade the nukes we have-and why that might be a dangerous idea.

Kevin finds a possible solution to his financial problems. Marco checks up on Meg's explanation for her suspicious behavior. Sally makes Eve an offer.

Serena hopes to win her third and finally Princess Key in order to go through to the master class but the competition is strong and one trainer has a Shiny Dragonair.

When Fluttershy's self-absorbed brother starts freeloading off their parents, she encourages him to move out, but he moves in with her instead, forcing Fluttershy to stand up to her brother and help him get over his fear of failure.

Elle is pressed into a corner by Hanssen, who wants to know who has been stealing drugs. After a shocking discovery, she is forced to choose between the good of the department and the people in it. Robyn and David's morality cafe proves a success, Rita pushes Iain away until a threatening incident makes her seek his help, and Cal urges Iain to try flirting with a patient, but his efforts go disastrously wrong.