"The Symmetric Cipher of Indigo Veins" follows Dr. Solana Zy Montrelle, a chromamancer investigating a series of murders in the floating city of Nyo Nola, where victims are found with perfect spiral patterns etched into their skin. When a renowned jazz trumpeter becomes the first victim, Solana partners with quantum AI specialist Orion Kofi Adeyemi to uncover a conspiracy involving melanin-based energy extraction.
The investigation leads them to the Celestial Spur, a mysterious quantum railway that crosses through different reality planes. With help from on Anansi, a sentient AI inhabiting a glass spider, they discover that venture-mystic Silas McCreary is harvesting the victims' melanin frequencies to create a private dimension outside time.
As more bodies appear, each corpse resonates with a specific musical note, forming parts of an ancient blues progression. Marina "Riff" Douglas, a street-wise chromamancer, helps decode these musical clues while evading the enigmatic Indigo Railman, whose true allegiance remains unclear.