-Starts 4 years after RotS. Krennic hunts down Galen who has been hiding since the end of Catalyst. He takes him into custody and forces him to work on the Death Star superlaser. Lyra Erso probably dies. Jyn is taken in by Saw Gerrera for a few years.
-Jyn starts living on her own at age 15, getting into trouble.
-19 years after RotS, Galen sends out a coded transmission that the Rebels intercept. Cassian Andor breaks Jyn out of prison on Wobani and brings her to Yavin IV where Mothma recruits her because of her connection to her father.
-Jyn, Cassian, and K2S0 travel to Jedha and meet the Imperial-turned-Rebel Bodhi Rook as well as Chirrut Imwe, who is a monk with the Guardians of the Whills, and his friend Baze Malbus. They fight a bunch of Stormtroopers. Sam's partisans may be involved? Jyn meets with Saw. Krennic shows off the Death Star by blowing up Saw's base, probably killing him. Maybe does a ton of damage to Jedha? Maybe a demonstration for Tarkin? Vader meets with Krennic at some point but who knows when.
-The Rebels return to Yavin IV where there's a big meeting. Some people want to give up, Jyn rallies them to fight.
-The Rebels strike Eadu to try to rescue Galen. He probably dies? Maybe this is where they find out the schematics are on Scariff.
-The prologue to ANH happens. The Rebel fleet attacks Scariff, with X-Wings disabling the shield gate that lets the troops get down below. Jyn, Cassian, and K2 sneak into the Imperial facility in disguises and capture the plans. They ultimately manage to broadcast them to the Tantive IV. Maybe a Leia cameo?
-During the battle, Chirrut dies. Most likely most of them or even all of them die, but he's the only one confirmed so far. Krennic almost certainly gets choked to death by Vader.