Here is a proposed mystery novel template / cheatsheet / outline / structure. As always, I’m always open to suggestions for how to improve it, so if you would like to share your ideas, just let me know!
Act One
Present the crime
Introduce the sleuth
Offer plausible suspects
Introduce crime complications
Introduce private life subplot
Act Two
Initial investigations and interrogations reveal clues
Disappearance of one suspect
Raise the stakes
Development of sub plot
Act Three
Reveal hidden motives of stakeholders
Unsatisfying solution reached
Return to overlooked clue from act one
Resolution of subplot
Confrontation with perpetrator
Resolution