Nightmare Fuel / Designated Survivor

Season 1

Pilot

• Before the episode ended, terrorists were able to wipe out the Capitol building, which is supposed to be one of the most secure places in Washington D.C. The burnt-out shell of the iconic Capitol Dome towering over that mass of smoking wreckage is both disorienting and horrific.
• Basically Kirkman's entire attitude, a man who never wanted to be President now having the fate of the world on his shoulders.

The First Day

• Innocent Muslims rounded up (and at least one beaten to death) simply for their religion. Worse in that the Governor of Michigan orders it as he feels even if they are innocent, they might know someone who is not — and he really believes he's more important than the President right now.
• Hannah's superior admits he's afraid to acknowledge her theory of more attacks coming because the idea of wiping out the U.S. government being the first step in a plan is terrifying.

The Mission

• If MacLeish is actually the mole, Kirkman is unknowingly contemplating placing him one heartbeat away from the Presidency.

The Interrogation

• A lone wolf terrorist managed to get through Secret Service security and breached White House grounds.

The Traitor

• The conspiracy behind the bombing is aware of Atwood's possible knowledge that Al-Sakar did not bomb the White House and has kidnapped his son to ensure his compliance. It's also implied the same may be true for MacLeish and his involvement.

The Results

• A single militia nutcase almost derails the election of a new Congress by poisoning a few polling stations with ricin, raising the fear that anyone who goes to vote could be killed.

The Blueprint

• Someone inside the Pentagon created a highly detailed three-dimensional simulation that exactly matches the devastation wrought by the Capitol bombing, and they did this a full three years before the in-universe date of the attack. Whatever the conspirators has been plotting has been in the works for quite a long time.
• Agent Wells is able to discover a photograph among the memorabilia of a former Army serviceman that links Congressman MacLeish and "Catalan" as being in the same military unit in Afghanistan. Shortly thereafter, Wells' allies in the FBI and CIA are able to find deeply buried information that this unit massacred hundreds of local civilians in retaliation for the deaths of a few of their own comrades at the hands of the Taliban — and the Pentagon whitewashed it all to make MacLeish into a war hero.
• Not long thereafter, Agent Wells is racing back into D.C. to bring this evidence to new Speaker Hookstraten and the rest of the committee reviewing MacLeish's nomination, when she is abruptly caught in a violent traffic accident.

The Oath

• We learn the fate of Agent Wells following her accident, and it's not pretty. She's been knocked unconscious with some pretty grisly head and torso injuries. The assailant who deliberately wrecked her car then tries to choke her to death. Fortunately, she's able to escape.
• It turns out that Charlie Langdon, President Richmond's Chief of Staff, is still alive and is in hiding from the Conspiracy. Agent Wells tries to get more information from him, but she's shot at by a gunman before she can learn anything more. Langdon also manages to escape, though.
• The previously mentioned three dimensional simulation of the Capitol bombing? The man who created it sent it to the Secretary of Defense, who was then ordered to reclassify it as top secret. Emily examines phone records and learns that the Secretary got a call from Chief of Staff Langdon's office who ordered him to reclassify it. Except Langdon wasn't in that day. The person who made that call was Aaron.
• Before being sworn in as VP, MacLeish is having some second thoughts about taking the oath. His wife, though, reassures him that he survived for a reason: so he could make America into an empire. She's either in on the Conspiracy, or she's got some ulterior motivations herself.
• And to cap it all off: the episode ends with the Conspiracy attempting to assassinate Kirkman. Agent Wells fires at the shooter and is able to throw off his aim, but Kirkman ends up seriously wounded.

The End of The Beginning

• Atwood confessed to a murder he didn't commit to get his kidnapped son back safely. Now he finds his son's body.

One Hundred Days

• The possible destruction of the Hoover Dam or The Golden Gate Bridge, which would mean the loss of thousands of peoples' lives. All the more so as one of them is actually considered a war crime if done deliberately during wartime.
• Also, The Conspiracy has people dedicated and committed enough that they are willing to die and/or kill other members of their ranks to prevent anyone from being able to find out what their end goal is.

Party Lines

• There is enough ordinance at the Conspiracy's secret base to, as Hannah Wells puts it, blow up three Capitol buildings.

Misalliance

• The sheer suddenness of Catalan gunning down Jason Atwood, right after he had gone to investigate what turned out to be only a deer.

Brace for Impact

• Patrick Lloyd, the mastermind behind the conspiracy has escaped from the authorities and has classified information about US defenses and vulnerabilities. America is at risk.

Season 2

Sting of the Tail

• Patrick Lloyd threatens to cover Washington, DC with a thousand kilograms of sarin gas.