Shadows picks up shortly after the Port Charles Hotel fire in 2004. If you remember correctly, at first, Zander was assumed dead in the fire, murdered by a blow to the head, which it was revealed that Elizabeth had inflicted. This story assumes that first story was the truth, and deals with the fallout.
It’s been about ten years since this storyline (!) so here are the pertinent details to remember about the rest of the characters: Elizabeth is pregnant with Cameron, she is still married to Ric, having remarried after the panic room. Carly and Sonny are in the middle of a very bad divorce. Jason and Courtney’s marriage is over, for reasons I don’t remember because I mostly pretend Courtney stopped doing anything after 2002, so I can still like her. Emily and Nikolas are together.
AJ is still out of town, having left after divorcing Courtney. (Without Lydia and embezzling money, because the head writer at the time, Bob Guza, was a dick and that was a stupid storyline. I’m a sucker for AJ). I’ve aged Michael for two reasons: storyline purposes and the kid in the picture below is my younger version of the current Michael (not Chad Duell, but Jackson Bond, a blonde-haired, brown-eyed boy who looks a lot like him)