What was the best part about writing a sequel?

I thought it would be not having to come up with backstories from scratch, but it turned out to be putting snippets in the sequel that a) were not truly necessary to understanding The Silent Cardinal but b) also gave folks who’d read The Hubley Case an extra nugget. There are a few arcs and tiebacks, character traits and quips in The Silent Cardinal that those readers told me they enjoyed.  That was really fun.