Murderer's chain

A financially desperate narrator plots to secure investment capital by hastening the inheritance of his wealthy, miserly mother-in-law and seeks a discreet method of murder. He learns of a lucrative off-world mining opportunity and, after rejecting crude assaults and poisons, encounters a Greenwich Village jeweler who offers a rare Martian necklace forged from an unfamiliar metal called Malutrex. Presented as a subtle, lethal implement known among Martians by a notorious name, the piece promises to accomplish the narrator's aims while raising questions about alien craftsmanship, secrecy surrounding new planets, and the moral cost of greed.