The plot of Archivist Wasp by Nicole Kornher-Stace asks what unfinished business might make effectively a superhero unable to find peace and pass on. Wasp, a desperately lonely archivist of ghost behavior, is tasked with finding out what happened to the world long ago from any ghost that might talk to her, in addition to fighting upstarts each year who want to take her life and her place.
But she meets the dangerous, unnamed ghost of a supersoldier on the hunt for someone he has lost in the underworld. And he thinks Wasp can help.