Time Traveling Blues in the City of the Watcher

All Aleck Woad wants to do is chill in his interdimensional Archive. Putter around with his collections of knickknacks from many worlds, scrawl in his notebooks, maybe take the occasional jaunt across the multiverse with his wife and partner-in-crime, Beth.
In the back of his mind, though, he has always been haunted by his first trip offworld as a teenager. He had unwittingly helped catalyze the bloody Battle of Melkhaios, in which hundreds of innocents were massacred. He had met his own future self, meddling with the battle, trying to stop it.
And he had seen his future self gunned down by the Reality Patrol.
He usually does his best not to think about it.
But one day, Aleck and Beth find themselves without warning back in Melkhaios. And they soon discover (as sometimes happens with interdimensional travel) that they have gone back in time, arriving sometime before young Aleck and the Battle.
This is Aleck's unexpected chance to undo the bloody events he witnessed as a youth - if he can change history before his own death catches up with him.
Unfortunately, changing your own past is easier said than done....