Edit: If you want to see a somewhat more detailed article, read here. However, I must warn you that there is a woeful lack of CAPS compared to mine...
The Most Essential Stuff
-There was a big BLACKOUT during which EVERY PERSON in the world LOST CONSCIOUSNESS. They all had a "FLASHFORWARD" which means they saw a flash of their own future.
-Everyone saw the same moment of the same day, and the visions match. (For example, if you saw yourself with someone, that person also saw you.) Nobody knows WHY this happened, and whether people can CHANGE their future or if it's set in stone.
-The FBI starts to INVESTIGATE the issue. The investigation is very painstaking, slow, and frustrating. Also for the viewers.
-The main characters are FBI investigator MARK and his wife OLIVIA. Mark is in charge of "Mosaic", the investigation of the blackouts. Olivia is a doctor. James' character will meet her first, so pay attention. Olivia looks like this.
-James' character is called GABRIEL MCDOW and he has had MULTIPLE FLASHFORWARDS, which is unheard of.
-Two people were AWAKE during the flashbacks, but nobody knows who they are. There's blurry video footage of one of them, known as SUSPECT ZERO.
-In her flashforward, Olivia saw herself in love with another man, the amusingly-named LLOYD SIMCOE. They hadn't met before the blackouts. Lloyd is British. He has an autistic son Olivia has been treating. He also believes he is somehow RESPONSIBLE for the blackouts, but this has not yet been explained. Olivia wants to save her marriage and not fall for Lloyd, but it's not going very well.
-Mark's flashforward had him investigating the case, and the clues from the vision keep showing up in the present. Also, he was talking on the phone with Lloyd, saying there will be ANOTHER BLACKOUT. Dun dun dun!
-Mark doesn't care about THE RULES and that's why he is SUSPENDED from the FBI. (He's also BROODING and ANGSTY, so what else is NEW?)
-There are lots of DRAMATIC CLOSE UPS and CLIFFHANGERS at the ends of episodes.
More Details Which May or May Not Matter for James' Character
-Mark, a recovering alcoholic, saw himself DRINKING in his vision. Oh yeah, and he was about to be killed, but the drinking has been more of an issue.
-Mark's AA sponsor AARON saw his dead soldier daughter alive in the flashforward. Then the daughter TRACEY showed up at his house, asking for protection. She's being chased by some organization. Aaron is also in DANGER.
-Lloyd has a buddy called SIMON who comes from England to be sarcastic and threaten him. Simon doesn't like the fact that Lloyd told people about their experiment. Simon is a doctor.
-Mark's work partner AGENT NOH didn't have a flashforward. He later found out he will be KILLED soon, and is trying to figure out the murder. Then they find out Mark is the one who's going to KILL him. Uh oh.
-Mark and Olivia have a daughter called CHARLIE. Her flashforward was "no more good days", but this hasn't been explained. Charlie recognized DYLAN, Lloyd's son, when she saw her at the hospital. Dylan, the autistic boy, is so far NOT PSYCHIC or anything.
-There is also a lesbian agent called JANIS who saw herself PREGNANT in the flashforward and an intern called BRYCE who has stage 4 CANCER and was going to kill himself, but decided to live because he saw a mysterious Asian woman in his vision. (Logically enough, Janis is looking into SPERM DONORS adn Bryce took a trip to ASIA.)
I think that's about the most important stuff. I'll edit with any new details, so people can KEEP UP. (Sorry about the CAPS but once you start talking like THIS, it's very hard to STOP.)