English jazz pianist who witnesses Helga Ulmann's murder. He investigates the killings with Gianna Brezzi, uncovers a hidden mural and a walled room, and ultimately confronts and defeats the true killer, Marta.
Helga's murder becomes the central case that drives Marcus's investigation.
Marcus sees the black-gloved figure attacking Helga through a window and rushes to her apartment after the murder.
They cooperate to trace the killings and uncover the hidden history behind them.
Gianna begins helping Marcus investigate after feeling guilty that her photograph identified him to the media.
Their friendship gives Marcus access to Carlo and later creates a painful mistaken suspicion.
The plot identifies Carlo as Marcus's heavy-drinking friend, and Marcus visits Carlo's home while investigating the murders.
Amanda's published research provides Marcus with a crucial investigative lead.
Marcus consults Amanda's modern folklore book and plans to visit her to learn more about the haunted house.
Marcus reconstructs Carlo's suppressed past through the child's drawing.
Marcus finds the school archive picture and realizes it matches the mural discovered in the abandoned house.
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