The mystery in question doesn’t necessarily need to be who is the murderer, as in this case it is largely “who is blackmailing the nurse?” Even “how does Blanc puzzle it out” qualifies it as a detective story itself.
It’s fair if you want a stricter definition but you are going to run into pushback on a personal definition.
The mystery in question specifically refers to a crime, usually a murder specifically and who committed it. Hence the “who” in “whodunit”. Thats why they don’t call it a “Whoisit” or “howdoeshe”
I’m sorry to tell you this but:
https://www.merriam-webster.com/dictionary/whodunit
The mystery in question doesn’t necessarily need to be who is the murderer, as in this case it is largely “who is blackmailing the nurse?” Even “how does Blanc puzzle it out” qualifies it as a detective story itself.
It’s fair if you want a stricter definition but you are going to run into pushback on a personal definition.
I’m sorry to burst your bubble but:
https://dictionary.cambridge.org/us/dictionary/english/whodunit
https://www.dictionary.com/browse/whodunit
https://www.collinsdictionary.com/us/dictionary/english/whodunit#%3A~%3Atext=(hudʌnɪt+)+also+whodunnit%2C[informal]
The mystery in question specifically refers to a crime, usually a murder specifically and who committed it. Hence the “who” in “whodunit”. Thats why they don’t call it a “Whoisit” or “howdoeshe”