I'm not sure if I have a brainstorming idea or a hair-brain Iddy.
I've read books that are divided into parts. What do you think of starting with one character in part one, moving on to the second character in part two, and then both characters in part three?

Char. #1 thinks she committed murder - abused housewife/Investigator Reporter, found by PI her sister-in-law
Char. #2 father stole a valuable diamond. had an affair with his dtr.-in-law, his son accused of murdering them both, but acquitted, and Diamond never recovered.

Both characters join, with their garbage at Seagate on Khiloi Point

This last contest sort of gave birth to this.

Chyrs