So I missed all of last season except for the the first few episodes.
What do I need to know to start this season?
If I can keep it all straight in my head ...
Tom Keen gets off the ship where Liz had held him captive and kills the shipyard guy who had been keeping it quiet for Liz. Liz gets pinned for the murder and The Cabal (the dudes running the world who don't like Red much but were leaving him alone because they thought he had incriminating evidence about them) orchestrates for her to be questioned under increasing scrutiny. Just when it looks like she's going to be charged, Red brings Tom out of hiding to testify on her behalf to get her off the hook. Then he escapes before
he's arrested.
So about that incriminating evidence The Cabal thinks Red has on them? He doesn't have it, but he knows it's in "the Fulcrum," which only Liz knows the location of, but she doesn't remember anything about her past, so Red hypnotizes her or some shit to jog her memory. It works, and Liz remembers where the Fulcrum is. The Fulcrum ends up being an old datatape that indeed has a bunch of incriminating information about The Cabal. It was hidden in Liz's teddy bear from when she was a kid.
Liz finds out her mother was a KGB spy and her real heritage is Russian. Her birth name is Masha Rostova. Liz shows a member of The Cabal that the Fulcrum exists, which puts her on their shitlist. They frame an assassination attempt and a bombing at the CIA's Russian office on her. A member of The Cabal, the U.S. attorney general, was behind this as well as convincing the head of Liz's FBI team, Cooper, into thinking that he was dying and needed a special medication that he wouldn't get if he didn't do everything The Cabal told him to do (shady shit throughout the season). Cooper and Liz confront him, and he says he'll dismantle the FBI team, get Liz put in jail, get Ressler kicked out of the FBI for an addiction to Oxycontin he conveniently developed that season, get Samar extradited to Iran for killing some Iran dudes, etc. So Liz shoots him to death. After killing the attorney general, she had to run away with Red so she wouldn't be arrested.
Now Cooper has been kicked off the team because he was present for the murder of the attorney general and did nothing to stop Liz from running away. Ressler is in charge of the team and he, Samar and Aram are chasing Red and Liz.
I think that basically catches you up.