Fiona Flanagan

Fiona "The Viper" Flanagan was a suspect during the murder investigation of distiller Davy Byrne in Blue Blazes (Case #21 of Mysteries of the Past). She then turned out to be The Scarlet Slayer, the killer of multiple prostitutes, including Gladys Perrin, in Death is a Cabaret (Case #23 of Mysteries of the Past). She was later murdered in Slayer's End (Case #24 of Mysteries of the Past).

Profile
Fiona was a 42-year-old Irish mobster and the sister of Irish gang leader Finley Flanagan. She had short brown hair and a scar under her left eye. She donned a white shirt with a maroon neckerchief, an olive green vest and a brown coat with pinstripes and black lapels with golden buttons on them. She also wore a bowler hat with a red stripe and earrings.

In her first appearance, it is made known that Fiona smoked cigarettes, went to horse races and read Pistols and Petticoats.

In her second appearance, it is discovered that she knew anatomy, saw Phantom of the Cabaret and drank coffee.

Blue Blazes
Fiona became a suspect into Davy's murder investigation after Maddie and the player found her flyer on a crate with moonshine bottles. Fiona said that if Davy worked for her, she would not kill him to avoid losing a chance to profit since he was a good distiller.

During the investigation, Fiona was reported to be dismantling Davy's distillery, compromising evidence. After the team stopped her, she left for the horse races.

The team had another talk with Fiona after finding a banshee she had sent to the victim. She claimed to have sent Davy the banshee after he tried to cheat her out of money to pay his wife's horse races debts, thus admitting he distilled moonshine for her gang. She made clear that she was not a damsel in distress to play with.

Fiona turned out to be innocent after Mauro Massetti was found responsible for the murder, but was confronted again when the team shut down Davy's distillery after finding proper evidence (a ledger detailing its monthly moonshine sales). Although she got mad at the team, she implied that she had other assets to take care of. Maddie then said that they would make sure to locate them.

Death is a Cabaret
Fiona became a suspect again after the player and Isaac found a checkbook belonging to her, which recently made a transaction to the victim. Despite the fact her brother ran the prostitute racket, Fiona said Gladys had a talent for making her customers thirsty, which was profitable for her. So naturally, Fiona decided to reward her, and had called her death a waste of talent and bad for business.

Fiona was spoken to again about a poster about the recent prohibition, with a message saying "Viper is going to the dogs", referring to her and her brother's gang names. When asked if this was cause enough for her to make her brother's business suffer like hers, Fiona called the allegations nothing more than a fantasy; considering how they share their profits, she would jeopardize her own income as well as Finley's. The Scarlet Slayer had been a nuisance to both of them, but when they have a problem they sit and talk about it, and they have to cooperate to in order to work well.

Despite that, it was eventually revealed that Fiona was the Scarlet Slayer, responsible for Gladys' murder on top of several others. Initially denying involvement, Fiona admitted to the crime. She killed Gladys and the other girls to liberate them from being employed as prostitutes. During the trial, Ramirez told Judge Lawson that Fiona escaped during her transfer to the court.

Murder details
Fiona was found strangled in an opium den. Per Dick, she was strangled with some sort of rope or wire, but not before putting up a fight. Under her nails, he found traces of Lavender Lust cream, which meant that the killer used Lavender Lust cream.

Inside Fiona's hideout, the team found a burned curtain string, which was filed as the murder weapon. The fire destroyed every trace of the killer, but Viola discovered that the rope was set alight with the oil from an opium lamp. This meant the killer smoked opium.

Killer and motives
The killer was revealed to be her brother, Irish gang leader Finley Flanagan, also known as Mad Dog.

After accidentally confessing to the murder, Finley said that he had taken care of his sister despite her bouts of criminal insanity. However, he could not help her when she started killing prostitutes. After she escaped custody and went to the opium den, she madly lashed out at Finley. Figuring out that Fiona was too far gone, he strangled her with a curtain rope out of mercy. In court, Judge Takakura took on the trial because of Judge Lawson's personal involvement in the case. He sentenced Finley to 25 years in Stonewall Prison.

Trivia

 * Fiona is one of the serial killers to appear in the game.
 * Fiona is one of the characters to appear as a suspect in two cases.
 * Fiona is the fifth of the few characters throughout the game to have appeared as a suspect, killer, and victim.
 * Fiona is one of the characters who make an appearance in the second-to-last case of a district as a suspect, only to be murdered in the very district's finale.
 * Fiona's death at the hands of her brother is one of the instances of domestic homicide in Mysteries of the Past.

Case appearances

 * Sinners and Saints (Case #19 of Mysteries of the Past; mentioned)
 * Eyes Wide Shut (Case #20 of Mysteries of the Past; mentioned)
 * Blue Blazes (Case #21 of Mysteries of the Past)
 * Death is a Cabaret (Case #23 of Mysteries of the Past)
 * Slayer's End (Case #24 of Mysteries of the Past)
 * Death Without Parole (Case #25 of Mysteries of the Past; mentioned)
 * 3:10 to Death (Case #28 of Mysteries of the Past; mentioned)