This is the sequel to Litany For A Broken World. The presumptive title is Every Sky a Stranger (Entangled Realities, book 2).
My current logline:
When an EMT with PTSD falls through a portal to an alternate version of Boston, three friends from different parts of the multiverse, each who have been helped by him, attempt a rescue, before conflicting memories destroy his mind.
Honestly, it's easier to write a whole novel than a 1 sentence description of it!