With Stoick a prisoner of the Berserkers, Hiccup is forced to ask Alvin for help. At the same time, the Screaming Death draws near...
Boyd targets the vulnerable Detroit mob, and Raylen gets involved with Crowe family members in Florida.
Tuffnut goes undercover to help the team rescue the Skrill from the Berserkers' grasp.
Chalky and Maitland hide out at his old mentor's, Oscar Boneau. Gillian contemplates selling her business for a life with Roy.
Still grieving for his brother, Al, in a fit of rage kills a policeman. Rothstein and Margaret unexpectedly run in to each other, and Willie drops out of college, enraging his father.
Certain that Alvin is planning an attack on Berk, Stoick institutes a ban on all dragon flying. Hiccup, certain that Alvin will be using his newfound dragon-training knowledge to bolster his attack, forms a secret “Dragon Flight Club” in order to train the kids to defend Berk against Alvin’s dragon army.moreless
Van Alden is ordered to keep an eye on the Capone's. Dr. Valentin Narcisse arrives in town with nothing but trouble with him. Eddie demands a promotion.
Rebecca gets to the bottom of the staff's fateful decision to air Jerry Dantana's special report on Operation Genoa.
Charlie, Mac, Jerry, Neal and Maggie conduct the first red team meeting for the story about Operation Genoa.
In the second part of the season finale, Li'l Gideon has managed to take possession of the Mystery Shack and unless the Pines family can somehow reacquire it, the fate of their beloved tourist trap is doomed.moreless
To get his hands on the deed to the Mystery Shack, Li'l Gideon summons Bill Cipher, a supernatural entity with the ability to steal a memory from a person's mind. This is part one of the two-part season finale.moreless
The gang search for Hiccup and Toothless, discovering that both are severe peril from the outcasts.
All the dragon species have multiple individuals except for Night Furies, Hiccup finds a secret page in the book of dragons revealing to him a secret island where other Night Furies live. Hiccup and Toothless embark on a challenging adventure to the island, but what may lie in his path, only one can guess.moreless
Because the vikings' homes can't support the weight of the dragons, they install metal perches above the homes. However when lightning keeps striking the village, Toothless gets blamed for angering the god Thor.moreless
As Capone's cavalry rides in, the war starts: With firepower on the one hand and scheming to alienate Masseria from Rosetti, Nucky fights to get his business back and keep his life.
Gillian takes on Gyp with her very own weapons, but sees herself overpowered; Richard poses as a one-man-army and seems to have more luck saving what's important.
Meanwhile, Margaret has run off to face difficult decisions – not only about her unborn baby, but also about the future of her marriage.moreless
Owen makes plans with Katie as well as with Margaret, but those will turn out a whole different way after Nucky sends him to take care of Joe. Nucky too makes promises to his wife, speaking of a better future while trying to sort out his current business situation – being troubled with this, he turns down Chalky, one of his few allies left. On the political side, Gaston takes further action.
Meanwhile, Gyp has to deal with the uncertainties of nature, and Nelson "George Muller" Van Alden with the nature of uncertain dealings.
Nucky himself reaches out for a powerful ally, while dealing with his mistress getting more attention than he's comfortable with. Meanwhile, Margaret has to concern herself not only with a living birthday present for her daughter, but also with some delicate feminine issues.
The women's health clinic Margaret wants to set up runs into trouble. Gillian must make some changes to stay afloat and Van Alden finally come clean to his wife.
The dragons become sick and the gang try to cure them.
Rothstein asks Gyp to be his new supplier but has other plans in mind. Gillian worries about her business.
Dipper gets unconformable with the fact that he is shorter than Mabel. So he searches for some magic that can make him grow. Then Gideon finds out about the magic and tries to tamper with their heights.moreless
With the dragons gone, Alvin and the outcasts are poised to attack.
Chalky tries to help his daughter, Maybelle. Nucky's emotional state leads to Gyp getting the upper hand. Eli gets out of prison, and Margaret's concerns on the sanitary condition of the hospital are not taken seriously.moreless
The dragons are falsely accused of vandalism and banished from Berk, leaving the island vulnerable to an attack by Alvin and the Outcasts.
With vikings and dragons now at peace, Gobber's role as weaponsmith is no longer needed. Hiccup tries to find him a new job.
The gang decide to visit a show starring Lil' Gideon, a psychic kid and Grunkle Stan's competitor, where he demonstrates his psychic powers. He falls in love with Mabel and invites her to meet him. She refuses to go, but also doesn't want to break his heart. But when Dipper persuades Mabel to go on a date with Gideon to question his genuineness, she soon learns he will lose his cuteness too quickly.moreless
With Amon in control of Republic City, Team Avatar hides, waiting for the United Forces to arrive. When they do, the Equalists show off their new weapon and defeat the United Forces quickly. General Iroh then joins Team Avatar in hiding. Planning their next move, Iroh decides that they must take out the air field to stop the Equalists. Bolin and Asami join General Iroh while Korra and Mako disguise themselves as Eqaulists and sneak onto Air Temple Island. On the island they come across a familiar face and discover the shocking truth about Amon's origins.moreless
Alicia defends a judge facing misconduct charges and Kalinda visits Lana Delaney. Meanwhile, Cary makes a career change.