(Spoilers, obviously.)
I haven’t seen the newest version of this story, but I have seen the one with Albert Finney and the one with David Suchet, so I know the wealth of happy or conflicted responses Poirot may have to this situation. But how about other great detectives?
Sam Vimes: Sam Vimes once personally fought off a revenge demon, so he’s not going to buy the ‘this man deserved death’ rhetoric and will arrest everyone. He will also, however, speak as a character witness at each of the murderers’ trials to vouch that they probably would never do something like this again. Vetinari pardons them all, and Sam throws up his hands wondering what was the point of anything.
Sherlock Holmes: Sherlock Holmes once accidentally completely intentionally murdered an abuser, so he’s probably going to be sensitive to this case. Not only would he let the killers go, he’d have Watson write a whole story about how a mafia assassin killed the guy and history would be none the wiser.
Phryne Fisher: She’d probably handle it like Poirot did (unless Jack was there to frown at her until she let him arrest people) but the bigger question is, who would she sleep with? I think it would be the young couple who are always played by the hottest people in the cast.
Philip Marlowe: Given his trouble with both the police and the mafia, his judgement on this issue will be rather clouded, and he’ll probably spend a night in jail as the suspect before the Transylvanian police let him out. On his way home, he will think back on the mystery, smack his head with his hand, and yell “GOD DAMN IT!”
Kinsey Millhone: Kinsey hates rich people slightly more than she hates herself, so she’ll turn them over to the police and reflect that most of the killers here are rich and will afford good lawyers, whereas if she killed a guy in cold blood she’d get forty years.
Sam Spade: Unless he was being paid to solve the mystery, I highly doubt Sam Spade would give a shit.