Behind the Mask is a case featured in Criminal Case as the twelfth case of Mysteries of the Past (Season 4) and the one-hundred eighty-third case overall. It is the final case to take place in the Elysium Fields district of Concordia.
Isaac and the player went to Alastor's party in the mansion in order to uncover his identity once and for all. Upon entering, Isaac got soaked when a guest fell into the pool. Angry, he went there with the player, only to find George Buchanan stabbed dead.
Mid-investigation, Maddie went to the party to go undercover but discovered the absinthe in the billiards room and got drunk. Later, journalist Katherine Woolf snuck into Evie's library. The team then found enough evidence to arrest Wentworth, Archie Rochester's valet, for the murder.
After admitting to the murder, Wentworth drank a bottle of poison to take Mr Alastor's secret to the grave. He later succumbed to the poison's effects before the team could find out more. The team then deduced that Wentworth would die only for Archie, his master.
District Attorney Justin Lawson and the player talked to Archie, who refused to admit to the accusations. They then searched the billiards room and found a piece of paper, which was a script of Alastor's admission of love to Giulietta Capecchi at the end of the party. Upon interrogation, Giulietta said she had thrown away Alastor's gift to her in the fountain, which Justin and the player found. According to Evie, the tiara box was purchased by Archie.
The two talked to Archie, who then admitted to being Alastor. He said that he had created the persona even before he met Giulietta in order to gain popularity. He then admitted that the recent murders were something special to woo Giulietta. Furthermore, he said that Wentworth had stabbed George with a champagne saber because he thought that his master would kill George himself for courting Giulietta. The two then placed him under arrest.
Meanwhile, Charlie went to Maddie to ask for an equipment she took while intoxicated in the airship. Upon getting the equipment back, Charlie finished his and Dick's Detection of Necessary Attributes (DNA) machine, which would help identify people based on biological traits. Afterwards, Charlie and Dick successfully tested the machine with Katherine's hair.
After the events, Chief Wright admitted that because he was not directly responsible for any crime, Archie had to be freed. He also said that Archie was being sent abroad by his parents, which greatly angered Justin. The next day, Charlie informed the team that they were able to submit the DNA machine in time and that they were to participate in the World Exhibition.
- George Buchanan (found stabbed in a swimming pool)
- Champagne Saber
- The killer snuffs tobacco.
- The killer plays billiards.
- The killer eats caviar.
- The killer wears a red peony.
- The killer wears yellow silk.
- Investigate Swimming Pool. (Clues: Bowl of Sweets, Victim's Body; Victim identified: George Buchanan)
- Examine Bowl of Sweets. (Result: Ring; New Suspect: Vittorio Capecchi)
- Talk to Vittorio Capecchi about the murder. (Prerequisite: Ring found; New Crime Scene Unlocked: Grand Hall)
- Investigate Grand Hall. (Prerequisite: Vittorio interrogated; Clues: Gold Cabinet, Keys)
- Examine Gold Cabinet. (Result: Bloody Blade)
- Analyze Bloody Blade. (09:00:00; Murder weapon registered: Champagne Saber; Attribute: The killer plays billiards)
- Examine Keys. (Result: Wentworth's Keys; New Suspect: Wentworth)
- Talk to Wentworth about his keys. (Prerequisite: Wentworth's Keys unraveled; New Suspect: Archie Rochester)
- Question Archie Rochester about this mansion. (Prerequisite: Wentworth interrogated)
- Autopsy Victim's Body. (18:00:00; Attribute: The killer snuffs tobacco)
- Go to Chapter 2. (No stars)
- Investigate Billiards Room. (Available after unlocking Chapter 2; Clues: Snuff Box, Wallet, Faded Letter)
- Examine Snuff Box. (Result: Brown Grains)
- Analyze Brown Grains. (12:00:00; Attribute: The killer eats caviar; New Crime Scene Unlocked: Poolside)
- Investigate Poolside. (Prerequisite: Brown Grains analyzed; Clues: Broken Statue, Cane)
- Examine Broken Statue. (Result: Wentworth's Bust)
- Ask Wentworth about the statue. (Prerequisite: Wentworth's Bust unraveled; Profiles updated: Wentworth plays billiards and eats caviar, Archie plays billiards and eats caviar)
- Examine Cane. (Result: Numbers and Figures)
- Analyze Numbers and Figures. (12:00:00)
- Confront Vittorio Capecchi about his dealings with the victim. (Prerequisite: Numbers and Figures analyzed; Profile updated: Vittorio snuffs tobacco)
- Examine Wallet. (Result: Woman's Face)
- Examine Woman's Face. (New Suspect: Katherine Woolf)
- Question Katherine Woolf about the victim. (Prerequisite: Katherine Woolf identified)
- Examine Faded Letter. (Result: Victim's Letter)
- Analyze Victim's Letter. (06:00:00; New Suspect: Giulietta Capecchi)
- Talk to Giulietta about the love letter. (Prerequisite: Victim's Letter analyzed)
- Go to Chapter 3. (No stars)
- Investigate Main Stairs. (Available after unlocking Chapter 3; Clues: Notebook, Newspaper Article, Broken Metal Pieces)
- Examine Notebook. (Result: Black Fluid)
- Examine Black Fluid. (Result: Newspaper Ink)
- Confront Katherine Woolf about her notes on the murders. (Prerequisite: Newspaper Ink identified under microscope; Profile updated: Katherine plays billiards)
- Examine Newspaper Article. (Result: Rochester's Name)
- Ask Archie about his family's feud with the victim. (Prerequisite: Rochester's Name decoded; Profiles updated: Archie snuffs tobacco, Wentworth snuffs tobacco)
- Examine Broken Metal Pieces. (Result: Copper Object)
- Analyze Copper Object. (09:00:00)
- Confront Giulietta about her death threat to the victim. (Prerequisite: Copper Object analyzed; Profile updated: Giulietta snuffs tobacco, plays billiards and eats caviar)
- Investigate Cosy Corner. (All tasks before must be done first; Clues: Saber Box, Broken Bottle)
- Examine Saber Box. (Result: Pink Powder)
- Analyze Pink Powder. (15:00:00; Attribute: The killer wears a red peony)
- Examine Broken Bottle. (Result: Bloody Fibers)
- Analyze Bloody Fibers. (09:00:00; Attribute: The killer wears yellow silk)
- Take care of the killer now!
- Go to All That Glitters... (6/6). (No stars)
All That Glitters... (6/6)
- Confront Archie about being Alastor. (Available after unlocking All That Glitters...)
- Investigate Billiards Room. (Prerequisite: Archie interrogated; Clue: Typewriter)
- Examine Typewriter. (Result: Alastor's Speech)
- Ask Giulietta about Alastor's message. (Prerequisite: Alastor's Speech unraveled)
- Investigate Grand Hall. (Prerequisite: Giulietta interrogated; Clue: Purple Box [Tiara Box])
- Examine Tiara Box. (Result: Numbers)
- Analyze Numbers. (06:00:00)
- Confront Archie with proof he's Alastor. (Prerequisite: Numbers analyzed; Reward: 20,000 Coins)
- See what Charlie wants. (Available after unlocking All That Glitters...)
- Investigate Swimming Pool. (Prerequisite: Charles interrogated; Clue: Broken Device)
- Examine Broken Device. (Result: Machine Part)
- Analyze Machine Part. (09:00:00)
- Talk to Dick about the DNA machine. (Prerequisite: Machine Part analyzed; Reward: Burger)
- Investigate Poolside. (Prerequisite: Dick interrogated; Clue: Hat)
- Examine Hat. (Result: Hair)
- Analyze Hair. (06:00:00)
- Check if the hat belongs to Katherine Woolf. (Prerequisite: Hair analyzed; Reward: Steampunk Hat)
- Move on to a new crime (in Century Mile)! (No stars)
- The case plot bears similarities to the 1925 novel The Great Gatsby:
- A murder occurs and the body is found in the pool.
- The killer of the murder victim commits suicide.
- The person who had pushed the killer into committing murder is able to escape, disillusioning someone to the concept of justice and wealth.
- The elusive party holder's motives are similar.
- The party is held in the party holder's mansion.
- Due to the story's canon, Judge Takakura does not make an appearance in this case.
- This is one of the cases in which Maddie and Isaac interact with each other.
- This is one of the four cases in Mysteries of the Past where the killer does not face trial, the other ones being Death is a Cabaret, Best Laid Plans, and Last Stand for Justice.